diff --git a/Library/Homebrew/refresh_brew.rb b/Library/Homebrew/refresh_brew.rb
index 753036ed55..bc61061a2a 100644
--- a/Library/Homebrew/refresh_brew.rb
+++ b/Library/Homebrew/refresh_brew.rb
@@ -25,12 +25,16 @@ class RefreshBrew
   end
   
   def current_revision
-    `#{REVISION_COMMAND}`.strip
+    in_prefix { `#{REVISION_COMMAND}`.strip }
   end
   
   private
   
+  def in_prefix
+    Dir.chdir(HOMEBREW_PREFIX) { yield }
+  end
+  
   def git_pull!
-    Dir.chdir(HOMEBREW_PREFIX) { `#{UPDATE_COMMAND}` }
+    in_prefix { `#{UPDATE_COMMAND}` }
   end
 end
\ No newline at end of file
diff --git a/Library/Homebrew/unittest.rb b/Library/Homebrew/unittest.rb
index bc1cc6937c..48e4650d44 100755
--- a/Library/Homebrew/unittest.rb
+++ b/Library/Homebrew/unittest.rb
@@ -502,41 +502,54 @@ class BeerTasting <Test::Unit::TestCase
   end
   
   def test_updater_update_homebrew_without_any_changes
-    updater = RefreshBrewMock.new
-    updater.in_prefix_expect("git pull origin masterbrew", "Already up-to-date.\n")
-    
-    assert_equal false, updater.update_from_masterbrew!
-    assert updater.updated_formulae.empty?
+    outside_prefix do
+      updater = RefreshBrewMock.new
+      updater.in_prefix_expect("git pull origin masterbrew", "Already up-to-date.\n")
+      
+      assert_equal false, updater.update_from_masterbrew!
+      assert updater.updated_formulae.empty?
+    end
   end
   
   def test_updater_update_homebrew_without_formulae_changes
-    updater = RefreshBrewMock.new
-    output = fixture('update_git_pull_output_without_formulae_changes')
-    updater.in_prefix_expect("git pull origin masterbrew", output)
-    
-    assert_equal true, updater.update_from_masterbrew!
-    assert !updater.pending_formulae_changes?
-    assert updater.updated_formulae.empty?
+    outside_prefix do
+      updater = RefreshBrewMock.new
+      output = fixture('update_git_pull_output_without_formulae_changes')
+      updater.in_prefix_expect("git pull origin masterbrew", output)
+      
+      assert_equal true, updater.update_from_masterbrew!
+      assert !updater.pending_formulae_changes?
+      assert updater.updated_formulae.empty?
+    end
   end
   
   def test_updater_update_homebrew_with_formulae_changes
-    updater = RefreshBrewMock.new
-    output = fixture('update_git_pull_output_with_formulae_changes')
-    updater.in_prefix_expect("git pull origin masterbrew", output)
-    
-    assert_equal true, updater.update_from_masterbrew!
-    assert updater.pending_formulae_changes?
-    assert_equal %w{ antiword bash-completion xar yajl }, updater.updated_formulae
+    outside_prefix do
+      updater = RefreshBrewMock.new
+      output = fixture('update_git_pull_output_with_formulae_changes')
+      updater.in_prefix_expect("git pull origin masterbrew", output)
+      
+      assert_equal true, updater.update_from_masterbrew!
+      assert updater.pending_formulae_changes?
+      assert_equal %w{ antiword bash-completion xar yajl }, updater.updated_formulae
+    end
   end
   
   def test_updater_returns_current_revision
-    updater = RefreshBrewMock.new
-    updater.in_prefix_expect('git log -l -1 --pretty=format:%H', 'the-revision-hash')
-    assert_equal 'the-revision-hash', updater.current_revision
+    outside_prefix do
+      updater = RefreshBrewMock.new
+      updater.in_prefix_expect('git log -l -1 --pretty=format:%H', 'the-revision-hash')
+      assert_equal 'the-revision-hash', updater.current_revision
+    end
   end
   
   private
   
+  OUTSIDE_PREFIX = '/tmp'
+  def outside_prefix
+    Dir.chdir(OUTSIDE_PREFIX) { yield }
+  end
+  
   def fixture(name)
     self.class.fixture_data[name]
   end