--- a/old-configure.in
+++ b/old-configure.in
@@ -6499,17 +6499,17 @@ if test "$MOZ_WIDGET_TOOLKIT" = "cocoa";
 fi
 
 MOZ_CONFIG_ICU()
 
 dnl ========================================================
 dnl mask as short hand property
 dnl ========================================================
 dnl Uncommenting the next line would enable mask-as-shorthand feature.
-dnl MOZ_ENABLE_MASK_AS_SHORTHAND=1
+MOZ_ENABLE_MASK_AS_SHORTHAND=1
 if test "$MOZ_ENABLE_MASK_AS_SHORTHAND"; then
   AC_DEFINE(MOZ_ENABLE_MASK_AS_SHORTHAND)
 fi
 AC_SUBST(MOZ_ENABLE_MASK_AS_SHORTHAND)
 
 # Avoid using obsolete NSPR features
 AC_DEFINE(NO_NSPR_10_SUPPORT)