diff --git a/Library/Homebrew/extend/ENV.rb b/Library/Homebrew/extend/ENV.rb
index b6240d8e37..b07e6d006d 100644
--- a/Library/Homebrew/extend/ENV.rb
+++ b/Library/Homebrew/extend/ENV.rb
@@ -9,8 +9,12 @@ module HomebrewEnvExtension
     delete('CLICOLOR_FORCE') # autotools doesn't like this
     remove_cc_etc
 
-    # Mountain Lion no longer ships a few .pcs; make sure we pick up our versions
     if MacOS.mountain_lion?
+      # Fix issue with sed barfing on unicode characters on Mountain Lion.
+      delete('LC_ALL')
+      self['LANG']="C"
+
+      # Mountain Lion no longer ships a few .pcs; make sure we pick up our versions
       prepend 'PKG_CONFIG_PATH',
         HOMEBREW_REPOSITORY/'Library/Homebrew/pkgconfig', ':'
     end