diff --git a/Rakefile b/Rakefile
index bdddb1d..4b16245 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,5 +1,7 @@
 # -*- ruby -*-
 
+ENV["LC_ALL"] = "C" if RUBY_PLATFORM =~ /darwin/
+
 desc "run regression tests"
 task "test" do
   sh "ruby -w run-regression.rb"