diff --git a/lib/ace/worker/worker_client.js b/lib/ace/worker/worker_client.js
index 2e0bd826..82800e10 100644
--- a/lib/ace/worker/worker_client.js
+++ b/lib/ace/worker/worker_client.js
@@ -51,7 +51,7 @@ var WorkerClient = function(topLevelNamespaces, packagedJs, mod, classname) {
     }
     else {
         var workerUrl;
-        if (require.supports.indexOf("ucjs2-pinf-0") >= 0) {
+        if (typeof require.supports !== "undefined" && require.supports.indexOf("ucjs2-pinf-0") >= 0) {
             // We are running in the sourcemint loader.
             workerUrl = require.nameToUrl("ace/worker/worker_sourcemint");
         } else {