diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 755555b4dc1..c9e33a9bad8 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -747,6 +747,8 @@ function ctrlNumberTabSelection(event)
 
 #ifdef XP_MACOSX
   if (!event.metaKey)
+#elifdef XP_UNIX
+  if (!event.altKey)
 #else
   if (!event.ctrlKey)
 #endif