diff --git a/Library/Homebrew/test/test_formula.rb b/Library/Homebrew/test/test_formula.rb
index a05fa46915..07da0aa32c 100644
--- a/Library/Homebrew/test/test_formula.rb
+++ b/Library/Homebrew/test/test_formula.rb
@@ -58,7 +58,7 @@ class FormulaTests < Homebrew::TestCase
     prefix.mkpath
     assert_equal prefix, f.installed_prefix
   ensure
-    prefix.rmtree
+    f.rack.rmtree
   end
 
   def test_installed_prefix_devel_installed
@@ -73,7 +73,7 @@ class FormulaTests < Homebrew::TestCase
     prefix.mkpath
     assert_equal prefix, f.installed_prefix
   ensure
-    prefix.rmtree
+    f.rack.rmtree
   end
 
   def test_installed_prefix_stable_installed
@@ -88,7 +88,7 @@ class FormulaTests < Homebrew::TestCase
     prefix.mkpath
     assert_equal prefix, f.installed_prefix
   ensure
-    prefix.rmtree
+    f.rack.rmtree
   end
 
   def test_installed_prefix_head_active_spec