diff --git a/Memola/Canvas/Contexts/GraphicContext.swift b/Memola/Canvas/Contexts/GraphicContext.swift
index 0ace6d9..9e5f594 100644
--- a/Memola/Canvas/Contexts/GraphicContext.swift
+++ b/Memola/Canvas/Contexts/GraphicContext.swift
@@ -13,7 +13,7 @@ import Foundation
 @objc(GraphicContext)
 class GraphicContext: NSManagedObject {
     @NSManaged var id: UUID
-    @NSManaged var canvas: Canvas
+    @NSManaged var canvas: Canvas?
     @NSManaged var strokes: NSMutableOrderedSet
 
     var currentStroke: Stroke?
diff --git a/Memola/Canvas/Core/Canvas.swift b/Memola/Canvas/Core/Canvas.swift
index 4f93c28..05a845a 100644
--- a/Memola/Canvas/Core/Canvas.swift
+++ b/Memola/Canvas/Core/Canvas.swift
@@ -15,7 +15,7 @@ class Canvas: NSManagedObject, Identifiable {
     @NSManaged var id: UUID
     @NSManaged var width: CGFloat
     @NSManaged var height: CGFloat
-    @NSManaged var memo: Memo
+    @NSManaged var memo: Memo?
     @NSManaged var graphicContext: GraphicContext
 
     let gridContext = GridContext()
@@ -43,8 +43,9 @@ class Canvas: NSManagedObject, Identifiable {
 extension Canvas {
     func load() {
         state = .loading
-        graphicContext.strokes.forEach {
-            ($0 as? Stroke)?.loadVertices()
+        graphicContext.strokes.forEach { stroke in
+            guard let stroke = stroke as? Stroke else { return }
+            stroke.loadVertices()
         }
         state = .loaded
     }
diff --git a/Memola/Features/Memos/MemosView.swift b/Memola/Features/Memos/MemosView.swift
index c52813a..4694446 100644
--- a/Memola/Features/Memos/MemosView.swift
+++ b/Memola/Features/Memos/MemosView.swift
@@ -31,6 +31,9 @@ struct MemosView: View {
         }
         .fullScreenCover(item: $memo) { memo in
             MemoView(canvas: memo.canvas)
+                .onDisappear {
+                    managedObjectContext.refreshAllObjects()
+                }
         }
     }
 
diff --git a/Memola/Persistence/Transformers/QuadValueTransformer.swift b/Memola/Persistence/Transformers/QuadValueTransformer.swift
index f03c9f3..63b03b3 100644
--- a/Memola/Persistence/Transformers/QuadValueTransformer.swift
+++ b/Memola/Persistence/Transformers/QuadValueTransformer.swift
@@ -22,7 +22,7 @@ class QuadValueTransformer: ValueTransformer {
             return nil
         }
         do {
-            let data = try JSONEncoder().encode(quads)
+            let data = try JSONEncoder().encode(quads.map(\.quad))
             return data
         } catch {
             print(error.localizedDescription)
@@ -37,8 +37,8 @@ class QuadValueTransformer: ValueTransformer {
             return nil
         }
         do {
-            let quads = try JSONDecoder().decode([StrokeQuad].self, from: data)
-            return quads
+            let quads = try JSONDecoder().decode([Quad].self, from: data)
+            return quads.map(StrokeQuad.init)
         } catch {
             print(error.localizedDescription)
             assertionFailure("[Memola] - Failed to transform `Data` to `Quad`")
diff --git a/Memola/Resources/Models/MemolaModel.xcdatamodeld/MemolaModel.xcdatamodel/contents b/Memola/Resources/Models/MemolaModel.xcdatamodeld/MemolaModel.xcdatamodel/contents
index 0592f91..89c2561 100644
--- a/Memola/Resources/Models/MemolaModel.xcdatamodeld/MemolaModel.xcdatamodel/contents
+++ b/Memola/Resources/Models/MemolaModel.xcdatamodeld/MemolaModel.xcdatamodel/contents
@@ -4,7 +4,7 @@
         <attribute name="height" attributeType="Double" defaultValueString="0.0" usesScalarValueType="YES" customClassName="CGFloat"/>
         <attribute name="id" attributeType="UUID" usesScalarValueType="NO"/>
         <attribute name="width" attributeType="Double" defaultValueString="0.0" usesScalarValueType="YES" customClassName="CGFloat"/>
-        <relationship name="graphicContext" maxCount="1" deletionRule="Cascade" destinationEntity="GraphicContext" inverseName="canvas" inverseEntity="GraphicContext"/>
+        <relationship name="graphicContext" optional="YES" maxCount="1" deletionRule="Cascade" destinationEntity="GraphicContext" inverseName="canvas" inverseEntity="GraphicContext"/>
         <relationship name="memo" maxCount="1" deletionRule="Deny" destinationEntity="Memo" inverseName="canvas" inverseEntity="Memo"/>
     </entity>
     <entity name="GraphicContext" representedClassName="GraphicContext" syncable="YES">