diff --git a/@sammo/server/src/worker_util.ts b/@sammo/server/src/worker_util.ts
index 4011cee..7334730 100644
--- a/@sammo/server/src/worker_util.ts
+++ b/@sammo/server/src/worker_util.ts
@@ -117,16 +117,23 @@ export class PortRPCClient<RPCL extends RPCLists> {
     public async callFunction<T extends keyof RPCL & string>(name: T, arg: Parameters<RPCL[T]>[0]): Promise<ReturnType<RPCL[T]>> {
         const id = this.prevID++;
 
+        let done = false;
+
         const waiter = new Promise((resolve, reject) => {
             const call: RawRPCCall = [name, id, arg];
             const callBuffer = ArrayBufferFromString(JSON.stringify(call));
 
             this.waiters.set(id, [resolve, reject]);
+            done = true;
             this.port.postMessage(callBuffer, [callBuffer]);
         });
 
         await delay(0);
 
+        if(!done){
+            throw new Error("RPC: callFunction failed");
+        }
+
         return waiter as Promise<ReturnType<RPCL[T]>>;
     }
 }