2 files changed, 4 insertions, 3 deletions
diff --git a/src/new_fields/Doc.ts b/src/new_fields/Doc.ts
index 7e02a5bc5..c2cfda079 100644
--- a/src/new_fields/Doc.ts
+++ b/src/new_fields/Doc.ts
@@ -186,7 +186,8 @@ export namespace Doc {
     }
 
     // compare whether documents or their protos match
-    export function AreProtosEqual(doc: Doc, other: Doc) {
+    export function AreProtosEqual(doc?: Doc, other?: Doc) {
+        if (!doc || !other) return false;
         let r = (doc === other);
         let r2 = (doc.proto === other);
         let r3 = (other.proto === doc);
diff --git a/src/new_fields/util.ts b/src/new_fields/util.ts
index fe0da2e7a..8cb1db953 100644
--- a/src/new_fields/util.ts
+++ b/src/new_fields/util.ts
@@ -6,7 +6,7 @@ import { FieldValue } from "./Types";
 import { RefField } from "./RefField";
 import { ObjectField } from "./ObjectField";
 import { action } from "mobx";
-import { Parent, OnUpdate, Update, Id } from "./FieldSymbols";
+import { Parent, OnUpdate, Update, Id, SelfProxy } from "./FieldSymbols";
 import { ComputedField } from "../fields/ScriptField";
 
 export const setter = action(function (target: any, prop: string | symbol | number, value: any, receiver: any): boolean {
@@ -86,7 +86,7 @@ export function deleteProperty(target: any, prop: string | number | symbol) {
         delete target[prop];
         return true;
     }
-    target[prop] = undefined;
+    target[SelfProxy][prop] = undefined;
     return true;
 }