diff --git a/core/app.js b/core/app.js
index 6a535a647..053013e7c 100644
--- a/core/app.js
+++ b/core/app.js
@@ -1,8 +1,5 @@
 import * as core from './core.js';
 
-let g_next_id = 1;
-let g_calls = {};
-
 let gSessionIndex = 0;
 
 /**
@@ -20,6 +17,8 @@ function makeSessionId() {
 function App() {
 	this._on_output = null;
 	this._send_queue = [];
+	this.calls = {};
+	this._next_call_id = 1;
 	return this;
 }
 
@@ -39,12 +38,12 @@ App.prototype.readOutput = function (callback) {
 App.prototype.makeFunction = function (api) {
 	let self = this;
 	let result = function () {
-		let id = g_next_id++;
-		while (!id || g_calls[id]) {
-			id = g_next_id++;
+		let id = self._next_call_id++;
+		while (!id || self.calls[id]) {
+			id = self._next_call_id++;
 		}
 		let promise = new Promise(function (resolve, reject) {
-			g_calls[id] = {resolve: resolve, reject: reject};
+			self.calls[id] = {resolve: resolve, reject: reject};
 		});
 		let message = {
 			message: 'tfrpc',
@@ -215,13 +214,19 @@ exports.app_socket = async function socket(request, response) {
 			} else if (message.action == 'createIdentity') {
 				await process.createIdentity();
 			} else if (message.message == 'tfrpc') {
-				if (message.id && g_calls[message.id]) {
-					if (message.error !== undefined) {
-						g_calls[message.id].reject(message.error);
-					} else {
-						g_calls[message.id].resolve(message.result);
+				if (message.id) {
+					let calls = process?.app?.calls;
+					if (calls) {
+						let call = calls[message.id];
+						if (call) {
+							if (message.error !== undefined) {
+								call.reject(message.error);
+							} else {
+								call.resolve(message.result);
+							}
+							delete calls[message.id];
+						}
 					}
-					delete g_calls[message.id];
 				}
 			} else {
 				if (process && process.eventHandlers['message']) {