diff --git a/packages/block/src/events/func_base.ts b/packages/block/src/events/func_base.ts
index ea2a60c2..17bac3ff 100644
--- a/packages/block/src/events/func_base.ts
+++ b/packages/block/src/events/func_base.ts
@@ -15,7 +15,7 @@ export class FuncBase extends Blockly.Events.Abstract {
   override isBlank: boolean = false;
 
   /** The procCode of procedure. */
-  protected procCode?: string;
+  procCode?: string;
 
   /**
    * @param procedure The procedure model.
diff --git a/packages/vm/src/engine/blocks.ts b/packages/vm/src/engine/blocks.ts
index aa79ad8b..09d6a35c 100644
--- a/packages/vm/src/engine/blocks.ts
+++ b/packages/vm/src/engine/blocks.ts
@@ -381,7 +381,8 @@ class Blocks {
         if (
             typeof (event as ClipCCBlock.Events.BlockBase).blockId !== 'string' &&
             typeof (event as ClipCCBlock.Events.VarBase).varId !== 'string' &&
-            typeof (event as ClipCCBlock.Events.CommentBase).commentId !== 'string'
+            typeof (event as ClipCCBlock.Events.CommentBase).commentId !== 'string' &&
+            typeof (event as ClipCCBlock.FuncChange).procCode !== 'string'
         ) {
             return;
         }
diff --git a/packages/vm/src/serialization/migration.js b/packages/vm/src/serialization/migration.js
index bc2057be..7989c4b8 100644
--- a/packages/vm/src/serialization/migration.js
+++ b/packages/vm/src/serialization/migration.js
@@ -102,7 +102,7 @@ const migrateMutation = (block, backward) => {
                 case 'return':
                 case 'generateshadows':
                     // Expect mutation[key] to be a string.
-                    mutation[key] = (mutation[key] === 'true');
+                    mutation[key] = typeof mutation[key] === 'string' ? (mutation[key] === 'true') : !!mutation[key];
                     break;
                 case 'argumentids':
                 case 'argumentnames':