diff --git a/platform/firefox/frameModule.js b/platform/firefox/frameModule.js
index a360d7168..98338e32f 100644
--- a/platform/firefox/frameModule.js
+++ b/platform/firefox/frameModule.js
@@ -183,14 +183,9 @@ const contentObserver = {
                 wantXHRConstructor: false
             });
 
-            sandbox.injectScript = function(script, evalCode) {
-                if ( evalCode ) {
-                    Cu.evalInSandbox(script, this);
-                    return;
-                }
-
-                Services.scriptloader.loadSubScript(script, this);
-            }.bind(sandbox);
+            sandbox.injectScript = function(script) {
+                Services.scriptloader.loadSubScript(script, sandbox);
+            };
         }
         else {
             sandbox = win;
@@ -200,43 +195,43 @@ const contentObserver = {
         sandbox.sendAsyncMessage = messager.sendAsyncMessage;
 
         sandbox.addMessageListener = function(callback) {
-            if ( this._messageListener_ ) {
-                this.removeMessageListener(
-                    this._sandboxId_,
-                    this._messageListener_
+            if ( sandbox._messageListener_ ) {
+                sandbox.removeMessageListener(
+                    sandbox._sandboxId_,
+                    sandbox._messageListener_
                 );
             }
 
-            this._messageListener_ = function(message) {
+            sandbox._messageListener_ = function(message) {
                 callback(message.data);
             };
 
             messager.addMessageListener(
-                this._sandboxId_,
-                this._messageListener_
+                sandbox._sandboxId_,
+                sandbox._messageListener_
             );
             messager.addMessageListener(
                 hostName + ':broadcast',
-                this._messageListener_
+                sandbox._messageListener_
             );
-        }.bind(sandbox);
+        };
 
         sandbox.removeMessageListener = function() {
             try {
                 messager.removeMessageListener(
-                    this._sandboxId_,
-                    this._messageListener_
+                    sandbox._sandboxId_,
+                    sandbox._messageListener_
                 );
                 messager.removeMessageListener(
                     hostName + ':broadcast',
-                    this._messageListener_
+                    sandbox._messageListener_
                 );
             } catch (ex) {
                 // It throws sometimes, mostly when the popup closes
             }
 
-            this._messageListener_ = null;
-        }.bind(sandbox);
+            sandbox._messageListener_ = null;
+        };
 
         return sandbox;
     },
diff --git a/platform/firefox/vapi-background.js b/platform/firefox/vapi-background.js
index 39207576a..9fec753d5 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -610,11 +610,11 @@ vAPI.tabs.injectScript = function(tabId, details, callback) {
         return;
     }
 
-    if ( details.file ) {
-        details.file = vAPI.getURL(details.file);
+    if ( typeof details.file !== 'string' ) {
+        return;
     }
 
-
+    details.file = vAPI.getURL(details.file);
     tab.linkedBrowser.messageManager.sendAsyncMessage(
         location.host + ':broadcast',
         JSON.stringify({
diff --git a/platform/firefox/vapi-client.js b/platform/firefox/vapi-client.js
index d11a84f9e..58bb110ca 100644
--- a/platform/firefox/vapi-client.js
+++ b/platform/firefox/vapi-client.js
@@ -96,7 +96,7 @@ vAPI.messaging = {
                     return;
                 }
 
-                self.injectScript(details.file || details.code, !details.file);
+                self.injectScript(details.file);
             }
         };
     },