diff --git a/server/python/rpc.py b/server/python/rpc.py
index 16db4eead..45515dbe8 100644
--- a/server/python/rpc.py
+++ b/server/python/rpc.py
@@ -72,7 +72,7 @@ class RpcProxy(object):
 
     def __setattr__(self, name: str, value: Any) -> None:
         if name == '__proxy_finalizer_id':
-            self.dict['__proxy_entry']['finalizerId'] = value
+            self.__dict__['__proxy_entry']['finalizerId'] = value
 
         return super().__setattr__(name, value)
 
@@ -241,7 +241,7 @@ class RpcPeer:
             if not proxy:
                 proxy = self.newProxy(__remote_proxy_id, __remote_constructor_name,
                                       __remote_proxy_props, __remote_proxy_oneway_methods)
-            proxy.__proxy_finalizer_id = __remote_proxy_finalizer_id
+            setattr(proxy, '__proxy_finalizer_id', __remote_proxy_finalizer_id)
             return proxy
 
         if __local_proxy_id:
diff --git a/server/src/rpc.ts b/server/src/rpc.ts
index b4503f74c..ef3dc044e 100644
--- a/server/src/rpc.ts
+++ b/server/src/rpc.ts
@@ -84,7 +84,7 @@ class RpcProxy implements PrimitiveProxyHandler<any> {
     }
 
     get(target: any, p: PropertyKey, receiver: any): any {
-        if (p === '__proxy_id')
+        if (p === RpcPeer.PROPERTY_PROXY_ID)
             return this.entry.id;
         if (p === '__proxy_constructor')
             return this.constructorName;
@@ -214,6 +214,10 @@ export class RpcPeer {
 
     static readonly finalizerIdSymbol = Symbol('rpcFinalizerId');
 
+    static isRpcProxy(value: any) {
+        return !!value?.[RpcPeer.PROPERTY_PROXY_ID];
+    }
+
     static getDefaultTransportSafeArgumentTypes() {
         const jsonSerializable = new Set<string>();
         jsonSerializable.add(Number.name);
@@ -242,6 +246,7 @@ export class RpcPeer {
         }
     }
 
+    static readonly PROPERTY_PROXY_ID = '__proxy_id';
     static readonly PROPERTY_PROXY_ONEWAY_METHODS = '__proxy_oneway_methods';
     static readonly PROPERTY_JSON_DISABLE_SERIALIZATION = '__json_disable_serialization';
     static readonly PROPERTY_PROXY_PROPERTIES = '__proxy_props';