diff --git a/Library/Homebrew/test/testing_env.rb b/Library/Homebrew/test/testing_env.rb
index f2a9fdce74..605cdfc5ca 100644
--- a/Library/Homebrew/test/testing_env.rb
+++ b/Library/Homebrew/test/testing_env.rb
@@ -14,7 +14,7 @@ require 'utils'
 require 'rbconfig'
 require 'tmpdir'
 
-tmpdir = Dir.mktmpdir
+tmpdir = Dir.mktmpdir("homebrew_tests")
 at_exit { FileUtils.remove_entry(tmpdir) }
 
 # Constants normally defined in global.rb