--- a/browser/base/content/browser.css
+++ b/browser/base/content/browser.css
@@ -243,26 +243,16 @@ toolbar[customizing] > .overflow-button 
   -moz-appearance: -moz-window-button-box;
 }
 
 %ifdef XP_MACOSX
 #titlebar-fullscreen-button {
   -moz-appearance: -moz-mac-fullscreen-button;
 }
 
-/* Because these buttons don't move, they should always be aligned the same,
- * left and right were deprecated, so we have to do work to get it to mean that: */
-#titlebar-buttonbox-container:-moz-locale-dir(ltr) {
-  -moz-box-align: start;
-}
-
-#titlebar-buttonbox-container:-moz-locale-dir(rtl) {
-  -moz-box-align: end;
-}
-
 /* Fullscreen and caption buttons don't move with RTL on OS X so override the automatic ordering. */
 #titlebar-secondary-buttonbox:-moz-locale-dir(ltr),
 #titlebar-buttonbox-container:-moz-locale-dir(rtl),
 .titlebar-placeholder[type="fullscreen-button"]:-moz-locale-dir(ltr),
 .titlebar-placeholder[type="caption-buttons"]:-moz-locale-dir(rtl) {
   -moz-box-ordinal-group: 1000;
 }