diff --git a/lib/ace/worker/worker.js b/lib/ace/worker/worker.js
index 102d8cd0..0e7270a3 100644
--- a/lib/ace/worker/worker.js
+++ b/lib/ace/worker/worker.js
@@ -30,6 +30,9 @@ var normalizeModule = function(parentId, moduleName) {
 };
 
 var require = function(parentId, id) {
+    if (!id.charAt)
+        throw new Error("worker.js require() accepts only (parentId, id) as arguments");
+
     var id = normalizeModule(parentId, id);
     
     var module = require.modules[id];