diff --git a/toolkit/components/extensions/ext-backgroundPage.js b/toolkit/components/extensions/ext-backgroundPage.js
index 464c1bae58cc..3ff04d07a013 100644
--- a/toolkit/components/extensions/ext-backgroundPage.js
+++ b/toolkit/components/extensions/ext-backgroundPage.js
@@ -37,7 +37,6 @@ BackgroundPage.prototype = {
     }
 
     let uri = Services.io.newURI(url, null, null);
-    let principal = this.extension.createPrincipal(uri);
 
     let system = Services.scriptSecurityManager.getSystemPrincipal();
     let interfaceRequestor = chromeWebNav.QueryInterface(Ci.nsIInterfaceRequestor);