diff --git a/.hgtags b/.hgtags
--- a/.hgtags
+++ b/.hgtags
@@ -8,8 +8,10 @@ 0b5f5c3d666be70d5a1fc9aea562d39adf8fa181
 7a5400416482ab079fd0073dafa0a5b0382d7eaf CHATZILLA_0_9_88_2_RELEASE
 fc5089117b1413b53ce57d201ed0005babbd3280 CHATZILLA_0_9_89_RELEASE
 7f32a1339f8c334b6d731ec4972faa7a412c1667 CHATZILLA_0_9_90_RELEASE
 22bcb0f2601112cf039e33f4faad9ce802a97b0e CHATZILLA_0_9_91_RELEASE
 b85ad0cda0507c587b1fc91872172c42b105876c CHATZILLA_0_9_91_1_RELEASE
 64c11fe5c5138ff2ca27578341840f645d21a783 SEA2_37_RELBRANCH
 21876a1c04b46d1c1e76f48a2015bced91afd7b7 CHATZILLA_0_9_92_RELEASE
 35ff2f0f2ad833481b3cdc35ac201c07b9508cff SEA2_42_RELBRANCH
+35ff2f0f2ad833481b3cdc35ac201c07b9508cff SEA2_42_RELBRANCH
+64823e8eb6d77e3dfc8a7aabf1ca12cb92f9d02f SEA2_42_RELBRANCH
diff --git a/xpi/makexpi.py b/xpi/makexpi.py
--- a/xpi/makexpi.py
+++ b/xpi/makexpi.py
@@ -150,17 +150,17 @@ def clean():
         if arg == 'clean':
             return True
     return False
 
 def locale():
     """
     check arguments for locale or return None
     """
-    locale_pattern = re.compile(r'\w{1,3}-\w{1,3}')
+    locale_pattern = re.compile(r'^[a-z]{1,3}(?:-[A-Z]{1,3}(?:-[a-z]{1,3})?)?$')
     for arg in sys.argv:
         locale_match = locale_pattern.match(arg)
         if locale_match is not None:
             return arg
     return None
 
 def version(fedir):
     """