diff --git a/platform/firefox/vapi-client.js b/platform/firefox/vapi-client.js
index 07e1ae65e..b5fd7d4c8 100644
--- a/platform/firefox/vapi-client.js
+++ b/platform/firefox/vapi-client.js
@@ -39,7 +39,7 @@ vAPI.sessionId = String.fromCharCode(Date.now() % 25 + 97) +
 /******************************************************************************/
 
 vAPI.setTimeout = vAPI.setTimeout || function(callback, delay) {
-    setTimeout(function() { callback(); }, delay);
+    return setTimeout(function() { callback(); }, delay);
 };
 
 /******************************************************************************/
diff --git a/platform/firefox/vapi-common.js b/platform/firefox/vapi-common.js
index fbd9cd75c..714a77e58 100644
--- a/platform/firefox/vapi-common.js
+++ b/platform/firefox/vapi-common.js
@@ -41,7 +41,7 @@ var vAPI = self.vAPI = self.vAPI || {};
 /******************************************************************************/
 
 vAPI.setTimeout = vAPI.setTimeout || function(callback, delay) {
-    setTimeout(function() { callback(); }, delay);
+    return setTimeout(function() { callback(); }, delay);
 };
 
 /******************************************************************************/