diff --git a/Library/Homebrew/cmd/test-bot.rb b/Library/Homebrew/cmd/test-bot.rb
index a30a85e6a7..516fb37568 100644
--- a/Library/Homebrew/cmd/test-bot.rb
+++ b/Library/Homebrew/cmd/test-bot.rb
@@ -285,6 +285,7 @@ module Homebrew
         @url = ENV["ghprbPullLink"]
         @hash = nil
         test "git", "checkout", "origin/master"
+        test "git", "clean", "-qxdff", "--exclude=/Library/Taps/"
       # Use Travis CI pull-request variables for pull request jobs.
       elsif travis_pr
         @url = "https://github.com/#{ENV["TRAVIS_REPO_SLUG"]}/pull/#{ENV["TRAVIS_PULL_REQUEST"]}"