diff --git a/runtime/pointers.ts b/runtime/pointers.ts
index 822b226..6d4cf9a 100644
--- a/runtime/pointers.ts
+++ b/runtime/pointers.ts
@@ -3887,7 +3887,12 @@ export class Pointer<T = any> extends Ref<T> {
                     if (is_array && Number(prop)+1==obj.length) Runtime.runtime_actions.trimArray(obj)
 
                     return true
-                }
+                },
+                ownKeys: (target) => {
+                    // assume that the whole object should be observed for transform
+                    this.handleBeforeNonReferencableGet();
+                    return Reflect.ownKeys(target);
+                },
             });
 
             // set right 'this' context for getters / setters
diff --git a/types/native_types.ts b/types/native_types.ts
index 438898a..dd0dc2d 100644
--- a/types/native_types.ts
+++ b/types/native_types.ts
@@ -181,7 +181,8 @@ Type.std.Set.setJSInterface({
     create_proxy: (value:Set<any>, pointer:Pointer) => {
         // override methods
         Object.defineProperty(value, "add", {value: el => {
-                return pointer.handleAdd(el);
+                if (value.has(el)) return false;
+                return pointer.handleAdd(el); // TODO: return the Set
             }, writable:false, enumerable:false});
 
         Object.defineProperty(value, "clear", {value: () => {
@@ -189,7 +190,8 @@ Type.std.Set.setJSInterface({
             }, writable:false, enumerable:false});
 
         Object.defineProperty(value, "delete", {value: el => {
-                return pointer.handleRemove(el);
+                if (!value.has(el)) return false;
+                return pointer.handleRemove(el); // TODO: return the Set
             }, writable:false, enumerable:false});
 
         /**** override getters to trigger handleBeforeValueGet(): ****/