diff --git a/pkl-cli/src/test/kotlin/org/pkl/cli/CliEvaluatorTest.kt b/pkl-cli/src/test/kotlin/org/pkl/cli/CliEvaluatorTest.kt
index f1586a2c..2ca85e72 100644
--- a/pkl-cli/src/test/kotlin/org/pkl/cli/CliEvaluatorTest.kt
+++ b/pkl-cli/src/test/kotlin/org/pkl/cli/CliEvaluatorTest.kt
@@ -1164,7 +1164,7 @@ result = someLib.x
     """
           .trimIndent()
       )
-    assertThat(tempDir.resolve("package-1")).doesNotExist()
+    assertThat(tempDir.resolve("package-2")).doesNotExist()
   }
 
   @Test
diff --git a/pkl-cli/src/test/kotlin/org/pkl/cli/CliPackageDownloaderTest.kt b/pkl-cli/src/test/kotlin/org/pkl/cli/CliPackageDownloaderTest.kt
index 08ebcf13..faf8522e 100644
--- a/pkl-cli/src/test/kotlin/org/pkl/cli/CliPackageDownloaderTest.kt
+++ b/pkl-cli/src/test/kotlin/org/pkl/cli/CliPackageDownloaderTest.kt
@@ -56,12 +56,12 @@ class CliPackageDownloaderTest {
         noTransitive = true
       )
     cmd.run()
-    assertThat(tempDir.resolve("package-1/localhost:0/birds@0.5.0/birds@0.5.0.zip")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/birds@0.5.0/birds@0.5.0.json")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/fruit@1.0.5/fruit@1.0.5.zip")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/fruit@1.0.5/fruit@1.0.5.json")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/fruit@1.1.0/fruit@1.1.0.zip")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/fruit@1.1.0/fruit@1.1.0.json")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/birds@0.5.0/birds@0.5.0.zip")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/birds@0.5.0/birds@0.5.0.json")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/fruit@1.0.5/fruit@1.0.5.zip")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/fruit@1.0.5/fruit@1.0.5.json")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/fruit@1.1.0/fruit@1.1.0.zip")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/fruit@1.1.0/fruit@1.1.0.json")).exists()
   }
 
   @Test
@@ -90,9 +90,9 @@ class CliPackageDownloaderTest {
         noTransitive = true
       )
     cmd.run()
-    assertThat(tempDir.resolve(".my-cache/package-1/localhost:0/birds@0.5.0/birds@0.5.0.zip"))
+    assertThat(tempDir.resolve(".my-cache/package-2/localhost(3a)0/birds@0.5.0/birds@0.5.0.zip"))
       .exists()
-    assertThat(tempDir.resolve(".my-cache/package-1/localhost:0/birds@0.5.0/birds@0.5.0.json"))
+    assertThat(tempDir.resolve(".my-cache/package-2/localhost(3a)0/birds@0.5.0/birds@0.5.0.json"))
       .exists()
   }
 
@@ -113,8 +113,8 @@ class CliPackageDownloaderTest {
         noTransitive = true
       )
     cmd.run()
-    assertThat(tempDir.resolve("package-1/localhost:0/birds@0.5.0/birds@0.5.0.zip")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/birds@0.5.0/birds@0.5.0.json")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/birds@0.5.0/birds@0.5.0.zip")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/birds@0.5.0/birds@0.5.0.json")).exists()
   }
 
   @Test
@@ -228,9 +228,9 @@ class CliPackageDownloaderTest {
         noTransitive = false
       )
       .run()
-    assertThat(tempDir.resolve("package-1/localhost:0/birds@0.5.0/birds@0.5.0.zip")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/birds@0.5.0/birds@0.5.0.json")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/fruit@1.0.5/fruit@1.0.5.zip")).exists()
-    assertThat(tempDir.resolve("package-1/localhost:0/fruit@1.0.5/fruit@1.0.5.json")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/birds@0.5.0/birds@0.5.0.zip")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/birds@0.5.0/birds@0.5.0.json")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/fruit@1.0.5/fruit@1.0.5.zip")).exists()
+    assertThat(tempDir.resolve("package-2/localhost(3a)0/fruit@1.0.5/fruit@1.0.5.json")).exists()
   }
 }
diff --git a/pkl-codegen-kotlin/src/main/kotlin/org/pkl/codegen/kotlin/KotlinCodeGenerator.kt b/pkl-codegen-kotlin/src/main/kotlin/org/pkl/codegen/kotlin/KotlinCodeGenerator.kt
index f2699e7e..8de61c5d 100644
--- a/pkl-codegen-kotlin/src/main/kotlin/org/pkl/codegen/kotlin/KotlinCodeGenerator.kt
+++ b/pkl-codegen-kotlin/src/main/kotlin/org/pkl/codegen/kotlin/KotlinCodeGenerator.kt
@@ -22,6 +22,7 @@ import java.net.URI
 import java.util.*
 import org.pkl.core.*
 import org.pkl.core.util.CodeGeneratorUtils
+import org.pkl.core.util.IoUtils
 
 data class KotlinCodegenOptions(
   /** The characters to use for indenting generated Kotlin code. */
@@ -89,7 +90,7 @@ class KotlinCodeGenerator(
 
   private val propertyFileName: String
     get() =
-      "resources/META-INF/org/pkl/config/java/mapper/classes/${moduleSchema.moduleName}.properties"
+      "resources/META-INF/org/pkl/config/java/mapper/classes/${IoUtils.encodePath(moduleSchema.moduleName)}.properties"
 
   private val propertiesFile: String
     get() {
@@ -195,7 +196,7 @@ class KotlinCodeGenerator(
     }
 
   private fun relativeOutputPathFor(moduleName: String): String {
-    val nameParts = moduleName.split(".")
+    val nameParts = moduleName.split(".").map(IoUtils::encodePath)
     val dirPath = nameParts.dropLast(1).joinToString("/")
     val fileName = nameParts.last().replaceFirstChar { it.titlecaseChar() }
     return if (dirPath.isEmpty()) {
diff --git a/pkl-codegen-kotlin/src/test/kotlin/org/pkl/codegen/kotlin/KotlinCodeGeneratorTest.kt b/pkl-codegen-kotlin/src/test/kotlin/org/pkl/codegen/kotlin/KotlinCodeGeneratorTest.kt
index e8fd0319..64c8ef4f 100644
--- a/pkl-codegen-kotlin/src/test/kotlin/org/pkl/codegen/kotlin/KotlinCodeGeneratorTest.kt
+++ b/pkl-codegen-kotlin/src/test/kotlin/org/pkl/codegen/kotlin/KotlinCodeGeneratorTest.kt
@@ -1501,6 +1501,24 @@ class KotlinCodeGeneratorTest {
     confirmSerDe(bigStruct)
   }
 
+  @Test
+  fun `encoded file paths`(@TempDir path: Path) {
+    val kotlinCode =
+      generateKotlinFiles(
+        path,
+        PklModule(
+          "FooBar.pkl",
+          """
+      module `Foo*Bar`
+      
+      someProp: String
+    """
+            .trimIndent()
+        )
+      )
+    assertThat(kotlinCode).containsKey("kotlin/Foo(2a)Bar.kt")
+  }
+
   private fun generateFiles(tempDir: Path, vararg pklModules: PklModule): Map<String, String> {
     val pklFiles = pklModules.map { it.writeToDisk(tempDir.resolve("pkl/${it.name}.pkl")) }
     val evaluator = Evaluator.preconfigured()
diff --git a/pkl-commons-test/src/main/kotlin/org/pkl/commons/test/PackageServer.kt b/pkl-commons-test/src/main/kotlin/org/pkl/commons/test/PackageServer.kt
index 0a9a279c..e5c26a04 100644
--- a/pkl-commons-test/src/main/kotlin/org/pkl/commons/test/PackageServer.kt
+++ b/pkl-commons-test/src/main/kotlin/org/pkl/commons/test/PackageServer.kt
@@ -51,7 +51,14 @@ class PackageServer : AutoCloseable {
     const val FRUIT_1_1_SHA = "8d982761d182f2185e4180c82190791d9a60c721cb3393bb2e946fab90131e8c"
 
     fun populateCacheDir(cacheDir: Path) {
-      val basePath = cacheDir.resolve("package-1/localhost:$PORT")
+      doPopulateCacheDir(cacheDir.resolve("package-2/localhost(3a)$PORT"))
+    }
+
+    fun populateLegacyCacheDir(cacheDir: Path) {
+      doPopulateCacheDir(cacheDir.resolve("package-1/localhost:$PORT"))
+    }
+
+    private fun doPopulateCacheDir(basePath: Path) {
       basePath.deleteRecursively()
       Files.walk(packagesDir).use { stream ->
         stream.forEach { source ->
diff --git a/pkl-config-java/src/main/java/org/pkl/config/java/mapper/ClassRegistry.java b/pkl-config-java/src/main/java/org/pkl/config/java/mapper/ClassRegistry.java
index e1e44786..25972842 100644
--- a/pkl-config-java/src/main/java/org/pkl/config/java/mapper/ClassRegistry.java
+++ b/pkl-config-java/src/main/java/org/pkl/config/java/mapper/ClassRegistry.java
@@ -22,6 +22,7 @@ import java.util.Properties;
 import java.util.Set;
 import org.pkl.config.java.InvalidMappingException;
 import org.pkl.core.PClassInfo;
+import org.pkl.core.util.IoUtils;
 import org.pkl.core.util.Nullable;
 
 /**
@@ -77,7 +78,7 @@ public class ClassRegistry {
       loadedModules.add(pklModuleName);
       var url =
           ClassRegistry.class.getResourceAsStream(
-              CLASSES_DIRECTORY + "/" + pklModuleName + ".properties");
+              CLASSES_DIRECTORY + "/" + IoUtils.encodePath(pklModuleName) + ".properties");
       if (url == null) {
         return;
       }
diff --git a/pkl-core/src/main/java/org/pkl/core/packages/PackageResolvers.java b/pkl-core/src/main/java/org/pkl/core/packages/PackageResolvers.java
index 7f645eb4..dbc3fd49 100644
--- a/pkl-core/src/main/java/org/pkl/core/packages/PackageResolvers.java
+++ b/pkl-core/src/main/java/org/pkl/core/packages/PackageResolvers.java
@@ -413,7 +413,7 @@ final class PackageResolvers {
 
     private final Path tmpDir;
 
-    private static final String CACHE_DIR_PREFIX = "package-1";
+    private static final String CACHE_DIR_PREFIX = "package-2";
 
     @GuardedBy("lock")
     private final EconomicMap<PackageUri, FileSystem> fileSystems = EconomicMaps.create();
@@ -438,12 +438,14 @@ final class PackageResolvers {
         return path;
       }
       var checksumIdx = path.lastIndexOf("::");
-      return path.substring(0, checksumIdx);
+      return IoUtils.encodePath(path.substring(0, checksumIdx));
     }
 
     private Path getRelativePath(PackageUri uri) {
       return Path.of(
-          CACHE_DIR_PREFIX, uri.getUri().getAuthority(), getEffectivePackageUriPath(uri));
+          CACHE_DIR_PREFIX,
+          IoUtils.encodePath(uri.getUri().getAuthority()),
+          getEffectivePackageUriPath(uri));
     }
 
     private String getLastSegmentName(PackageUri packageUri) {
diff --git a/pkl-core/src/main/java/org/pkl/core/util/IoUtils.java b/pkl-core/src/main/java/org/pkl/core/util/IoUtils.java
index 9849b8d8..a5da3df2 100644
--- a/pkl-core/src/main/java/org/pkl/core/util/IoUtils.java
+++ b/pkl-core/src/main/java/org/pkl/core/util/IoUtils.java
@@ -597,6 +597,30 @@ public final class IoUtils {
     return newUri;
   }
 
+  /**
+   * Windows reserves characters {@code <>:"\|?*} in filenames.
+   *
+   * <p>For any such characters, enclose their decimal character code with parentheses. Verbatim
+   * {@code (} is encoded as {@code ((}.
+   */
+  public static String encodePath(String path) {
+    if (path.isEmpty()) return path;
+    var sb = new StringBuilder();
+    for (var i = 0; i < path.length(); i++) {
+      var character = path.charAt(i);
+      switch (character) {
+        case '<', '>', ':', '"', '\\', '|', '?', '*' -> {
+          sb.append('(');
+          sb.append(ByteArrayUtils.toHex(new byte[] {(byte) character}));
+          sb.append(")");
+        }
+        case '(' -> sb.append("((");
+        default -> sb.append(path.charAt(i));
+      }
+    }
+    return sb.toString();
+  }
+
   private static int getExclamationMarkIndex(String jarUri) {
     var index = jarUri.indexOf('!');
     if (index == -1) {
diff --git a/pkl-core/src/test/kotlin/org/pkl/core/util/IoUtilsTest.kt b/pkl-core/src/test/kotlin/org/pkl/core/util/IoUtilsTest.kt
index c795cc2c..1e169df8 100644
--- a/pkl-core/src/test/kotlin/org/pkl/core/util/IoUtilsTest.kt
+++ b/pkl-core/src/test/kotlin/org/pkl/core/util/IoUtilsTest.kt
@@ -431,4 +431,14 @@ class IoUtilsTest {
       IoUtils.readString(URI("http://example.com").toURL())
     }
   }
+
+  @Test
+  fun `encodePath encodes characters reserved on windows`() {
+    assertThat(IoUtils.encodePath("foo:bar")).isEqualTo("foo(3a)bar")
+    assertThat(IoUtils.encodePath("<>:\"\\|?*")).isEqualTo("(3c)(3e)(3a)(22)(5c)(7c)(3f)(2a)")
+    assertThat(IoUtils.encodePath("foo(3a)bar")).isEqualTo("foo((3a)bar")
+    assertThat(IoUtils.encodePath("(")).isEqualTo("((")
+    assertThat(IoUtils.encodePath("3a)")).isEqualTo("3a)")
+    assertThat(IoUtils.encodePath("foo/bar/baz")).isEqualTo("foo/bar/baz")
+  }
 }
diff --git a/pkl-doc/src/main/kotlin/org/pkl/doc/DocGenerator.kt b/pkl-doc/src/main/kotlin/org/pkl/doc/DocGenerator.kt
index 675727e6..05bd25a7 100644
--- a/pkl-doc/src/main/kotlin/org/pkl/doc/DocGenerator.kt
+++ b/pkl-doc/src/main/kotlin/org/pkl/doc/DocGenerator.kt
@@ -121,7 +121,7 @@ class DocGenerator(
 
   private fun createSymlinks(currentPackagesData: List<PackageData>) {
     for (packageData in currentPackagesData) {
-      val basePath = outputDir.resolve(packageData.ref.pkg)
+      val basePath = outputDir.resolve(packageData.ref.pkg.pathEncoded)
       val src = basePath.resolve(packageData.ref.version)
       val dest = basePath.resolve("current")
       if (dest.exists() && dest.isSameFileAs(src)) continue
diff --git a/pkl-doc/src/main/kotlin/org/pkl/doc/DocPackageInfo.kt b/pkl-doc/src/main/kotlin/org/pkl/doc/DocPackageInfo.kt
index 24d64836..a4d343c0 100644
--- a/pkl-doc/src/main/kotlin/org/pkl/doc/DocPackageInfo.kt
+++ b/pkl-doc/src/main/kotlin/org/pkl/doc/DocPackageInfo.kt
@@ -203,9 +203,9 @@ data class DocPackageInfo(
       when {
         !moduleName.startsWith(prefix) -> null
         else -> {
-          val modulePath = moduleName.substring(prefix.length).replace('.', '/')
+          val modulePath = moduleName.substring(prefix.length).replace('.', '/').pathEncoded
           if (documentation == null) {
-            "$name/$version/$modulePath/index.html".toUri()
+            "${name.pathEncoded}/$version/$modulePath/index.html".toUri()
           } else {
             documentation.resolve("$modulePath/index.html")
           }
diff --git a/pkl-doc/src/main/kotlin/org/pkl/doc/DocScope.kt b/pkl-doc/src/main/kotlin/org/pkl/doc/DocScope.kt
index ed799cae..30ca4b7f 100644
--- a/pkl-doc/src/main/kotlin/org/pkl/doc/DocScope.kt
+++ b/pkl-doc/src/main/kotlin/org/pkl/doc/DocScope.kt
@@ -71,10 +71,7 @@ internal sealed class DocScope {
   fun resolveModuleNameToRelativeDocUrl(name: String): URI? =
     resolveModuleNameToDocUrl(name)?.let { IoUtils.relativize(it, url) }
 
-  abstract fun resolveModuleNameToSourceUrl(
-    name: String,
-    sourceLocation: Member.SourceLocation
-  ): URI?
+  abstract fun resolveModuleNameToSourceUrl(name: String, sourceLocation: SourceLocation): URI?
 
   /** Resolves the given method name relative to this scope. */
   abstract fun resolveMethod(name: String): MethodScope?
@@ -207,10 +204,7 @@ internal class SiteScope(
       else -> null
     }
 
-  override fun resolveModuleNameToSourceUrl(
-    name: String,
-    sourceLocation: Member.SourceLocation
-  ): URI? =
+  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: SourceLocation): URI? =
     when {
       name.startsWith("pkl.") -> {
         val path = "/stdlib/${name.substring(4)}.pkl"
@@ -253,7 +247,9 @@ internal class PackageScope(
   private val moduleScopes: Map<String, ModuleScope> by lazy {
     modules.associate { module ->
       val docUrl =
-        url.resolve(getModulePath(module.moduleName, modulePrefix).uriEncoded + "/index.html")
+        url.resolve(
+          getModulePath(module.moduleName, modulePrefix).pathEncoded.uriEncoded + "/index.html"
+        )
       module.moduleName to ModuleScope(module, docUrl, this)
     }
   }
@@ -262,9 +258,11 @@ internal class PackageScope(
     ModuleScope(pklBaseModule, resolveModuleNameToDocUrl("pkl.base")!!, null)
   }
 
-  override val url: URI by lazy { parent.url.resolve("./$name/$version/index.html") }
+  override val url: URI by lazy { parent.url.resolve("./${name.pathEncoded}/$version/index.html") }
 
-  override val dataUrl: URI by lazy { parent.url.resolve("./data/$name/$version/index.js") }
+  override val dataUrl: URI by lazy {
+    parent.url.resolve("./data/${name.pathEncoded}/$version/index.js")
+  }
 
   fun getModule(name: String): ModuleScope = moduleScopes.getValue(name)
 
@@ -387,11 +385,11 @@ internal class ClassScope(
   override val url: URI by lazy {
     // `isModuleClass` distinction is relevant when this scope is a link target
     if (clazz.isModuleClass) parentUrl
-    else parentUrl.resolve("${clazz.simpleName.uriEncodedComponent}.html")
+    else parentUrl.resolve("${clazz.simpleName.pathEncoded.uriEncodedComponent}.html")
   }
 
   override val dataUrl: URI by lazy {
-    parent!!.dataUrl.resolve("${clazz.simpleName.uriEncodedComponent}.js")
+    parent!!.dataUrl.resolve("${clazz.simpleName.pathEncoded.uriEncodedComponent}.js")
   }
 
   override fun getMethod(name: String): MethodScope? =
@@ -403,10 +401,8 @@ internal class ClassScope(
   override fun resolveModuleNameToDocUrl(name: String): URI? =
     parent!!.resolveModuleNameToDocUrl(name)
 
-  override fun resolveModuleNameToSourceUrl(
-    name: String,
-    sourceLocation: Member.SourceLocation
-  ): URI? = parent!!.resolveModuleNameToSourceUrl(name, sourceLocation)
+  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: SourceLocation): URI? =
+    parent!!.resolveModuleNameToSourceUrl(name, sourceLocation)
 
   override fun resolveMethod(name: String): MethodScope? =
     clazz.methods[name]?.let { MethodScope(it, this) }
@@ -438,7 +434,7 @@ internal class TypeAliasScope(
     // only used for page scopes
     throw UnsupportedOperationException("resolveModuleNameToDocUrl")
 
-  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: Member.SourceLocation) =
+  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: SourceLocation) =
     // only used for page scopes
     throw UnsupportedOperationException("resolveModuleNameToSourceUrl")
 
@@ -464,7 +460,7 @@ internal class MethodScope(val method: PClass.Method, override val parent: DocSc
     // only used for page scopes
     throw UnsupportedOperationException("resolveModuleNameToDocUrl")
 
-  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: Member.SourceLocation) =
+  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: SourceLocation) =
     // only used for page scopes
     throw UnsupportedOperationException("resolveModuleNameToSourceUrl")
 
@@ -494,7 +490,7 @@ internal class PropertyScope(
     // only used for page scopes
     throw UnsupportedOperationException("resolveModuleNameToDocUrl")
 
-  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: Member.SourceLocation) =
+  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: SourceLocation) =
     // only used for page scopes
     throw UnsupportedOperationException("resolveModuleNameToSourceUrl")
 
@@ -525,7 +521,7 @@ internal class ParameterScope(val name: String, override val parent: DocScope) :
     // only used for page scopes
     throw UnsupportedOperationException("resolveModuleNameToDocUrl")
 
-  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: Member.SourceLocation) =
+  override fun resolveModuleNameToSourceUrl(name: String, sourceLocation: SourceLocation) =
     // only used for page scopes
     throw UnsupportedOperationException("resolveModuleNameToSourceUrl")
 
diff --git a/pkl-doc/src/main/kotlin/org/pkl/doc/PackageDataGenerator.kt b/pkl-doc/src/main/kotlin/org/pkl/doc/PackageDataGenerator.kt
index bbeaf7f3..7b7b7e43 100644
--- a/pkl-doc/src/main/kotlin/org/pkl/doc/PackageDataGenerator.kt
+++ b/pkl-doc/src/main/kotlin/org/pkl/doc/PackageDataGenerator.kt
@@ -37,9 +37,11 @@ import org.pkl.core.util.IoUtils
 internal class PackageDataGenerator(private val outputDir: Path) {
   fun generate(pkg: DocPackage) {
     val path =
-      outputDir.resolve(pkg.name).resolve(pkg.version).resolve("package-data.json").apply {
-        createParentDirectories()
-      }
+      outputDir
+        .resolve(pkg.name.pathEncoded)
+        .resolve(pkg.version)
+        .resolve("package-data.json")
+        .apply { createParentDirectories() }
     PackageData(pkg).write(path)
   }
 
diff --git a/pkl-doc/src/main/kotlin/org/pkl/doc/RuntimeDataGenerator.kt b/pkl-doc/src/main/kotlin/org/pkl/doc/RuntimeDataGenerator.kt
index 0d3e079a..90af5166 100644
--- a/pkl-doc/src/main/kotlin/org/pkl/doc/RuntimeDataGenerator.kt
+++ b/pkl-doc/src/main/kotlin/org/pkl/doc/RuntimeDataGenerator.kt
@@ -82,60 +82,71 @@ internal class RuntimeDataGenerator(
   }
 
   private fun writePackageFile(ref: PackageRef) {
-    outputDir.resolve("data/${ref.pkg}/${ref.version}/index.js").jsonWriter().use { writer ->
-      writer.isLenient = true
-      writer.writeLinks(
-        HtmlConstants.KNOWN_VERSIONS,
-        packageVersions.getOrDefault(ref.pkg, setOf()).sortedWith(descendingVersionComparator),
-        { it },
-        { if (it == ref.version) null else ref.copy(version = it).pageUrlRelativeTo(ref) },
-        { if (it == ref.version) CssConstants.CURRENT_VERSION else null }
-      )
-      writer.writeLinks(
-        HtmlConstants.KNOWN_USAGES,
-        packageUsages.getOrDefault(ref, setOf()).packagesWithHighestVersions().sortedBy { it.pkg },
-        PackageRef::pkg,
-        { it.pageUrlRelativeTo(ref) },
-        { null }
-      )
-    }
+    outputDir
+      .resolve("data/${ref.pkg.pathEncoded}/${ref.version.pathEncoded}/index.js")
+      .jsonWriter()
+      .use { writer ->
+        writer.isLenient = true
+        writer.writeLinks(
+          HtmlConstants.KNOWN_VERSIONS,
+          packageVersions.getOrDefault(ref.pkg, setOf()).sortedWith(descendingVersionComparator),
+          { it },
+          { if (it == ref.version) null else ref.copy(version = it).pageUrlRelativeTo(ref) },
+          { if (it == ref.version) CssConstants.CURRENT_VERSION else null }
+        )
+        writer.writeLinks(
+          HtmlConstants.KNOWN_USAGES,
+          packageUsages.getOrDefault(ref, setOf()).packagesWithHighestVersions().sortedBy {
+            it.pkg
+          },
+          PackageRef::pkg,
+          { it.pageUrlRelativeTo(ref) },
+          { null }
+        )
+      }
   }
 
   private fun writeModuleFile(ref: ModuleRef) {
-    outputDir.resolve("data/${ref.pkg}/${ref.version}/${ref.module}/index.js").jsonWriter().use {
-      writer ->
-      writer.isLenient = true
-      writer.writeLinks(
-        HtmlConstants.KNOWN_VERSIONS,
-        moduleVersions.getOrDefault(ref.id, setOf()).sortedWith(descendingVersionComparator),
-        { it },
-        { if (it == ref.version) null else ref.copy(version = it).pageUrlRelativeTo(ref) },
-        { if (it == ref.version) CssConstants.CURRENT_VERSION else null }
+    outputDir
+      .resolve(
+        "data/${ref.pkg.pathEncoded}/${ref.version.pathEncoded}/${ref.module.pathEncoded}/index.js"
       )
-      writer.writeLinks(
-        HtmlConstants.KNOWN_USAGES,
-        typeUsages.getOrDefault(ref.moduleClassRef, setOf()).typesWithHighestVersions().sortedBy {
-          it.displayName
-        },
-        TypeRef::displayName,
-        { it.pageUrlRelativeTo(ref) },
-        { null }
-      )
-      writer.writeLinks(
-        HtmlConstants.KNOWN_SUBTYPES,
-        subtypes.getOrDefault(ref.moduleClassRef, setOf()).typesWithHighestVersions().sortedBy {
-          it.displayName
-        },
-        TypeRef::displayName,
-        { it.pageUrlRelativeTo(ref) },
-        { null }
-      )
-    }
+      .jsonWriter()
+      .use { writer ->
+        writer.isLenient = true
+        writer.writeLinks(
+          HtmlConstants.KNOWN_VERSIONS,
+          moduleVersions.getOrDefault(ref.id, setOf()).sortedWith(descendingVersionComparator),
+          { it },
+          { if (it == ref.version) null else ref.copy(version = it).pageUrlRelativeTo(ref) },
+          { if (it == ref.version) CssConstants.CURRENT_VERSION else null }
+        )
+        writer.writeLinks(
+          HtmlConstants.KNOWN_USAGES,
+          typeUsages.getOrDefault(ref.moduleClassRef, setOf()).typesWithHighestVersions().sortedBy {
+            it.displayName
+          },
+          TypeRef::displayName,
+          { it.pageUrlRelativeTo(ref) },
+          { null }
+        )
+        writer.writeLinks(
+          HtmlConstants.KNOWN_SUBTYPES,
+          subtypes.getOrDefault(ref.moduleClassRef, setOf()).typesWithHighestVersions().sortedBy {
+            it.displayName
+          },
+          TypeRef::displayName,
+          { it.pageUrlRelativeTo(ref) },
+          { null }
+        )
+      }
   }
 
   private fun writeClassFile(ref: TypeRef) {
     outputDir
-      .resolve("data/${ref.pkg}/${ref.version}/${ref.module}/${ref.type}.js")
+      .resolve(
+        "data/${ref.pkg.pathEncoded}/${ref.version.pathEncoded}/${ref.module.pathEncoded}/${ref.type.pathEncoded}.js"
+      )
       .jsonWriter()
       .use { writer ->
         writer.isLenient = true
diff --git a/pkl-doc/src/main/kotlin/org/pkl/doc/SearchIndexGenerator.kt b/pkl-doc/src/main/kotlin/org/pkl/doc/SearchIndexGenerator.kt
index 6ae1b710..d177315c 100644
--- a/pkl-doc/src/main/kotlin/org/pkl/doc/SearchIndexGenerator.kt
+++ b/pkl-doc/src/main/kotlin/org/pkl/doc/SearchIndexGenerator.kt
@@ -64,7 +64,7 @@ internal class SearchIndexGenerator(private val outputDir: Path) {
   fun generate(docPackage: DocPackage) {
     val path =
       outputDir
-        .resolve("${docPackage.name}/${docPackage.version}/search-index.js")
+        .resolve("${docPackage.name.pathEncoded}/${docPackage.version}/search-index.js")
         .createParentDirectories()
     JsonWriter(path.bufferedWriter()).use { writer ->
       writer.apply {
diff --git a/pkl-doc/src/main/kotlin/org/pkl/doc/Util.kt b/pkl-doc/src/main/kotlin/org/pkl/doc/Util.kt
index cb1b1556..63f55ff5 100644
--- a/pkl-doc/src/main/kotlin/org/pkl/doc/Util.kt
+++ b/pkl-doc/src/main/kotlin/org/pkl/doc/Util.kt
@@ -17,14 +17,13 @@ package org.pkl.doc
 
 import java.io.InputStream
 import java.net.URI
-import java.net.URLEncoder
-import java.nio.charset.StandardCharsets
 import java.nio.file.Path
 import kotlin.io.path.bufferedWriter
 import kotlin.io.path.outputStream
 import org.pkl.commons.createParentDirectories
 import org.pkl.core.*
 import org.pkl.core.parser.Lexer
+import org.pkl.core.util.IoUtils
 import org.pkl.core.util.json.JsonWriter
 
 // overwrites any existing file
@@ -148,3 +147,6 @@ internal val String.asModuleName: String
 
 internal val String.asIdentifier: String
   get() = Lexer.maybeQuoteIdentifier(this)
+
+internal val String.pathEncoded
+  get(): String = IoUtils.encodePath(this)
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/birds/0.5.0/Bird/index.js b/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/birds/0.5.0/Bird/index.js
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/birds/0.5.0/Bird/index.js
rename to pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/birds/0.5.0/Bird/index.js
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/birds/0.5.0/allFruit/index.js b/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/birds/0.5.0/allFruit/index.js
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/birds/0.5.0/allFruit/index.js
rename to pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/birds/0.5.0/allFruit/index.js
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/birds/0.5.0/catalog/index.js b/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/birds/0.5.0/catalog/index.js
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/birds/0.5.0/catalog/index.js
rename to pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/birds/0.5.0/catalog/index.js
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/birds/0.5.0/index.js b/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/birds/0.5.0/index.js
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/birds/0.5.0/index.js
rename to pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/birds/0.5.0/index.js
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/fruit/1.1.0/Fruit/index.js b/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/fruit/1.1.0/Fruit/index.js
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/fruit/1.1.0/Fruit/index.js
rename to pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/fruit/1.1.0/Fruit/index.js
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/fruit/1.1.0/index.js b/pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/fruit/1.1.0/index.js
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost:0/fruit/1.1.0/index.js
rename to pkl-doc/src/test/files/DocGeneratorTest/output/data/localhost(3a)0/fruit/1.1.0/index.js
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/index.html b/pkl-doc/src/test/files/DocGeneratorTest/output/index.html
index 0227712e..12c3df64 100644
--- a/pkl-doc/src/test/files/DocGeneratorTest/output/index.html
+++ b/pkl-doc/src/test/files/DocGeneratorTest/output/index.html
@@ -114,7 +114,7 @@ age: Int
                 <div class="member-modifiers">package </div>
               </div>
               <div class="member-main">
-                <div class="member-signature"><a class="name-decl" href="./localhost:0/birds/current/index.html">localhost:0/birds</a></div>
+                <div class="member-signature"><a class="name-decl" href="./localhost(3a)0/birds/current/index.html">localhost:0/birds</a></div>
               </div>
             </div>
           </li>
@@ -125,7 +125,7 @@ age: Int
                 <div class="member-modifiers">package </div>
               </div>
               <div class="member-main">
-                <div class="member-signature"><a class="name-decl" href="./localhost:0/fruit/current/index.html">localhost:0/fruit</a></div>
+                <div class="member-signature"><a class="name-decl" href="./localhost(3a)0/fruit/current/index.html">localhost:0/fruit</a></div>
               </div>
             </div>
           </li>
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/Bird/index.html b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/Bird/index.html
similarity index 99%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/Bird/index.html
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/Bird/index.html
index 6cd9c8d3..8329ca76 100644
--- a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/Bird/index.html
+++ b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/Bird/index.html
@@ -4,7 +4,7 @@
     <title>Bird (localhost:0/birds:0.5.0) • Docsite Title</title>
     <script src="../../../../scripts/pkldoc.js" defer="defer"></script>
     <script src="../../../../scripts/scroll-into-view.min.js" defer="defer"></script>
-    <script src="../../../../data/localhost:0/birds/0.5.0/Bird/index.js" defer="defer"></script>
+    <script src="../../../../data/localhost(3a)0/birds/0.5.0/Bird/index.js" defer="defer"></script>
     <link href="../../../../styles/pkldoc.css" media="screen" type="text/css" rel="stylesheet">
     <link rel="icon" type="image/svg+xml" href="../../../../images/favicon.svg">
     <link rel="apple-touch-icon" sizes="180x180" href="../../../../images/apple-touch-icon.png">
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/allFruit/index.html b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/allFruit/index.html
similarity index 99%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/allFruit/index.html
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/allFruit/index.html
index 6ae6e88a..99a908c7 100644
--- a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/allFruit/index.html
+++ b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/allFruit/index.html
@@ -4,7 +4,7 @@
     <title>allFruit (localhost:0/birds:0.5.0) • Docsite Title</title>
     <script src="../../../../scripts/pkldoc.js" defer="defer"></script>
     <script src="../../../../scripts/scroll-into-view.min.js" defer="defer"></script>
-    <script src="../../../../data/localhost:0/birds/0.5.0/allFruit/index.js" defer="defer"></script>
+    <script src="../../../../data/localhost(3a)0/birds/0.5.0/allFruit/index.js" defer="defer"></script>
     <link href="../../../../styles/pkldoc.css" media="screen" type="text/css" rel="stylesheet">
     <link rel="icon" type="image/svg+xml" href="../../../../images/favicon.svg">
     <link rel="apple-touch-icon" sizes="180x180" href="../../../../images/apple-touch-icon.png">
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/catalog/index.html b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/catalog/index.html
similarity index 99%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/catalog/index.html
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/catalog/index.html
index 214dedbe..9216f84c 100644
--- a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/catalog/index.html
+++ b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/catalog/index.html
@@ -4,7 +4,7 @@
     <title>catalog (localhost:0/birds:0.5.0) • Docsite Title</title>
     <script src="../../../../scripts/pkldoc.js" defer="defer"></script>
     <script src="../../../../scripts/scroll-into-view.min.js" defer="defer"></script>
-    <script src="../../../../data/localhost:0/birds/0.5.0/catalog/index.js" defer="defer"></script>
+    <script src="../../../../data/localhost(3a)0/birds/0.5.0/catalog/index.js" defer="defer"></script>
     <link href="../../../../styles/pkldoc.css" media="screen" type="text/css" rel="stylesheet">
     <link rel="icon" type="image/svg+xml" href="../../../../images/favicon.svg">
     <link rel="apple-touch-icon" sizes="180x180" href="../../../../images/apple-touch-icon.png">
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/index.html b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/index.html
similarity index 98%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/index.html
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/index.html
index fa374a60..7ab44551 100644
--- a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/index.html
+++ b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/index.html
@@ -4,7 +4,7 @@
     <title>localhost:0/birds (0.5.0) • Docsite Title</title>
     <script src="../../../scripts/pkldoc.js" defer="defer"></script>
     <script src="../../../scripts/scroll-into-view.min.js" defer="defer"></script>
-    <script src="../../../data/localhost:0/birds/0.5.0/index.js" defer="defer"></script>
+    <script src="../../../data/localhost(3a)0/birds/0.5.0/index.js" defer="defer"></script>
     <link href="../../../styles/pkldoc.css" media="screen" type="text/css" rel="stylesheet">
     <link rel="icon" type="image/svg+xml" href="../../../images/favicon.svg">
     <link rel="apple-touch-icon" sizes="180x180" href="../../../images/apple-touch-icon.png">
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/package-data.json b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/package-data.json
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/package-data.json
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/package-data.json
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/search-index.js b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/search-index.js
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/0.5.0/search-index.js
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/0.5.0/search-index.js
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/current b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/current
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/birds/current
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/birds/current
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/Fruit/index.html b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/Fruit/index.html
similarity index 99%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/Fruit/index.html
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/Fruit/index.html
index f41bd986..7c8aeb6a 100644
--- a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/Fruit/index.html
+++ b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/Fruit/index.html
@@ -4,7 +4,7 @@
     <title>Fruit (localhost:0/fruit:1.1.0) • Docsite Title</title>
     <script src="../../../../scripts/pkldoc.js" defer="defer"></script>
     <script src="../../../../scripts/scroll-into-view.min.js" defer="defer"></script>
-    <script src="../../../../data/localhost:0/fruit/1.1.0/Fruit/index.js" defer="defer"></script>
+    <script src="../../../../data/localhost(3a)0/fruit/1.1.0/Fruit/index.js" defer="defer"></script>
     <link href="../../../../styles/pkldoc.css" media="screen" type="text/css" rel="stylesheet">
     <link rel="icon" type="image/svg+xml" href="../../../../images/favicon.svg">
     <link rel="apple-touch-icon" sizes="180x180" href="../../../../images/apple-touch-icon.png">
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/index.html b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/index.html
similarity index 97%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/index.html
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/index.html
index 96d1ae8d..f9bd5009 100644
--- a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/index.html
+++ b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/index.html
@@ -4,7 +4,7 @@
     <title>localhost:0/fruit (1.1.0) • Docsite Title</title>
     <script src="../../../scripts/pkldoc.js" defer="defer"></script>
     <script src="../../../scripts/scroll-into-view.min.js" defer="defer"></script>
-    <script src="../../../data/localhost:0/fruit/1.1.0/index.js" defer="defer"></script>
+    <script src="../../../data/localhost(3a)0/fruit/1.1.0/index.js" defer="defer"></script>
     <link href="../../../styles/pkldoc.css" media="screen" type="text/css" rel="stylesheet">
     <link rel="icon" type="image/svg+xml" href="../../../images/favicon.svg">
     <link rel="apple-touch-icon" sizes="180x180" href="../../../images/apple-touch-icon.png">
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/package-data.json b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/package-data.json
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/package-data.json
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/package-data.json
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/search-index.js b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/search-index.js
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/1.1.0/search-index.js
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/1.1.0/search-index.js
diff --git a/pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/current b/pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/current
similarity index 100%
rename from pkl-doc/src/test/files/DocGeneratorTest/output/localhost:0/fruit/current
rename to pkl-doc/src/test/files/DocGeneratorTest/output/localhost(3a)0/fruit/current
diff --git a/pkl-executor/src/test/kotlin/org/pkl/executor/EmbeddedExecutorTest.kt b/pkl-executor/src/test/kotlin/org/pkl/executor/EmbeddedExecutorTest.kt
index 86c57ccf..97b85d0d 100644
--- a/pkl-executor/src/test/kotlin/org/pkl/executor/EmbeddedExecutorTest.kt
+++ b/pkl-executor/src/test/kotlin/org/pkl/executor/EmbeddedExecutorTest.kt
@@ -2,8 +2,11 @@ package org.pkl.executor
 
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.AfterAll
+import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertThrows
+import org.junit.jupiter.api.condition.DisabledOnOs
+import org.junit.jupiter.api.condition.OS
 import org.junit.jupiter.api.io.TempDir
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.MethodSource
@@ -424,9 +427,11 @@ class EmbeddedExecutorTest {
 
   @ParameterizedTest
   @MethodSource("getAllTestExecutors")
+  @DisabledOnOs(OS.WINDOWS, disabledReason = "Can't populate legacy cache dir on Windows")
   fun `evaluate a project dependency`(executor: TestExecutor, @TempDir tempDir: Path) {
     val cacheDir = tempDir.resolve("packages")
     PackageServer.populateCacheDir(cacheDir)
+    PackageServer.populateLegacyCacheDir(cacheDir)
     val projectDir = tempDir.resolve("project/")
     projectDir.createDirectories()
     projectDir.resolve("PklProject").toFile().writeText("""