diff --git a/pkl-core/src/main/java/org/pkl/core/ast/type/UnresolvedTypeNode.java b/pkl-core/src/main/java/org/pkl/core/ast/type/UnresolvedTypeNode.java
index 0d387b91f..22544d37b 100644
--- a/pkl-core/src/main/java/org/pkl/core/ast/type/UnresolvedTypeNode.java
+++ b/pkl-core/src/main/java/org/pkl/core/ast/type/UnresolvedTypeNode.java
@@ -39,7 +39,7 @@ public abstract class UnresolvedTypeNode extends PklNode {
 
     private final VmLanguage language;
     @Child UnresolvedTypeNode childNode;
-    TypeConstraintNode[] constraintCheckNodes;
+    @Children TypeConstraintNode[] constraintCheckNodes;
 
     public Constrained(
         SourceSection sourceSection,
diff --git a/pkl-core/src/main/java/org/pkl/core/runtime/VmTypeAlias.java b/pkl-core/src/main/java/org/pkl/core/runtime/VmTypeAlias.java
index b0f82a931..4f4feea84 100644
--- a/pkl-core/src/main/java/org/pkl/core/runtime/VmTypeAlias.java
+++ b/pkl-core/src/main/java/org/pkl/core/runtime/VmTypeAlias.java
@@ -184,7 +184,7 @@ public final class VmTypeAlias extends VmValue {
     // * Fewer root nodes to call
     // * ControlFlowException used to implement union types doesn't escape root node
 
-    if (typeParameters.isEmpty()) return (TypeNode) typeNode.deepCopy();
+    if (typeParameters.isEmpty()) return deepCopy(typeNode);
 
     // handle if alias root is itself a type variable (https://github.com/apple/pkl/issues/1711)
     if (typeNode instanceof TypeVariableNode typeVarNode) {
@@ -198,13 +198,11 @@ public final class VmTypeAlias extends VmValue {
     clone.accept(
         node -> {
           if (node instanceof TypeVariableNode typeVarNode) {
-            int index = typeVarNode.getTypeParameterIndex();
-            // should not need to clone type argument node because it is not used by its original
-            // root node
+            var index = typeVarNode.getTypeParameterIndex();
             node.replace(
                 typeArgumentNodes.length == 0
                     ? new UnknownTypeNode(sourceSection)
-                    : typeArgumentNodes[index]);
+                    : deepCopy(typeArgumentNodes[index]));
           } else if (node instanceof UnresolvedTypeNode.TypeVariable unresolvedTypeVar) {
             // Type variables inside constraint expressions (e.g. `every((it) -> it is T)`)
             // are still unresolved at instantiation time. Replace them with a resolved
@@ -213,7 +211,8 @@ public final class VmTypeAlias extends VmValue {
             node.replace(
                 typeArgumentNodes.length == 0
                     ? new UnresolvedTypeNode.Unknown(sourceSection)
-                    : new UnresolvedTypeNode.Resolved(sourceSection, typeArgumentNodes[index]));
+                    : new UnresolvedTypeNode.Resolved(
+                        sourceSection, deepCopy(typeArgumentNodes[index])));
           }
           return true;
         });
@@ -311,4 +310,8 @@ public final class VmTypeAlias extends VmValue {
   public String toString() {
     return qualifiedName.startsWith("pkl.base#") ? simpleName : qualifiedName;
   }
+
+  private static TypeNode deepCopy(TypeNode typeArgumentNode) {
+    return (TypeNode) typeArgumentNode.deepCopy();
+  }
 }
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/types/typeAliasConstraint3.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/types/typeAliasConstraint3.pkl
index 5f5a16741..de03ed6e5 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/input/types/typeAliasConstraint3.pkl
+++ b/pkl-core/src/test/files/LanguageSnippetTests/input/types/typeAliasConstraint3.pkl
@@ -1,3 +1,17 @@
-typealias MyList<T> = List(this[0] is T)
+import "pkl:test"
 
-foo: MyList<Int> = List("uh oh")
+typealias MyList<T> = List(this[0] is T)
+typealias MyList2<T> = List((this[0] as T) != null)
+typealias MyList3<T> = List((this[0] is Any(this is T)))
+typealias MyList4<T> = List((this[0] is T(!(this is T))))
+typealias MyList5<T> = List((this[0] is T(true)))
+typealias MyList6<T> = List(this[0] is T?)
+
+local foo = List("uh oh")
+
+res = test.catch(() -> foo as MyList<Int>)
+res2 = test.catch(() -> foo as MyList2<Int>)
+res3 = test.catch(() -> foo as MyList3<Int>)
+res4 = test.catch(() -> foo as MyList4<String>)
+res5 = test.catch(() -> foo as MyList5<Int>)
+res6 = test.catch(() -> foo as MyList6<Int>)
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasConstraint3.err b/pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasConstraint3.err
deleted file mode 100644
index aafc48d7d..000000000
--- a/pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasConstraint3.err
+++ /dev/null
@@ -1,25 +0,0 @@
-–– Pkl Error ––
-Type constraint `this[0] is T` violated.
-Value: List("uh oh")
-
-    this[0] is T
-    │   │   │
-    │   │   false
-    │   "uh oh"
-    List("uh oh")
-
-x | typealias MyList<T> = List(this[0] is T)
-                               ^^^^^^^^^^^^
-at typeAliasConstraint3#foo (file:///$snippetsDir/input/types/typeAliasConstraint3.pkl)
-
-x | foo: MyList<Int> = List("uh oh")
-                       ^^^^^^^^^^^^^
-at typeAliasConstraint3#foo (file:///$snippetsDir/input/types/typeAliasConstraint3.pkl)
-
-xxx | renderer.renderDocument(value)
-      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-at pkl.base#Module.output.text (pkl:base)
-
-xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
-                                                                         ^^^^
-at pkl.base#Module.output.bytes (pkl:base)
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasConstraint3.pcf b/pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasConstraint3.pcf
new file mode 100644
index 000000000..fbcf432c9
--- /dev/null
+++ b/pkl-core/src/test/files/LanguageSnippetTests/output/types/typeAliasConstraint3.pcf
@@ -0,0 +1,6 @@
+res = "Type constraint `this[0] is T` violated. Value: List(\"uh oh\")"
+res2 = "Expected value of type `Int`, but got type `String`. Value: \"uh oh\""
+res3 = "Type constraint `this[0] is Any(this is T)` violated. Value: \"u\""
+res4 = "Type constraint `this[0] is T(!(this is T))` violated. Value: \"u\""
+res5 = "Type constraint `this[0] is T(true)` violated. Value: List(\"uh oh\")"
+res6 = "Type constraint `this[0] is T?` violated. Value: List(\"uh oh\")"