diff --git a/Library/Homebrew/mktemp.rb b/Library/Homebrew/mktemp.rb
index 0127327189..ea3e767bdd 100644
--- a/Library/Homebrew/mktemp.rb
+++ b/Library/Homebrew/mktemp.rb
@@ -47,13 +47,13 @@ class Mktemp
 
   def run
     prefix_name = @prefix.tr "@", "AT"
-    if retain_in_cache?
-      source_dir = "#{HOMEBREW_CACHE}/Sources/#{prefix_name}"
-      @tmpdir = Pathname.new(source_dir)
-      chmod_rm_rf(@tmpdir) # clear out previous (otherwise not sure what happens)
-      FileUtils.mkdir_p(source_dir)
+    @tmpdir = if retain_in_cache?
+      tmpdir = HOMEBREW_CACHE/"Sources/#{prefix_name}"
+      chmod_rm_rf(tmpdir) # clear out previous staging directory
+      tmpdir.parent.mkpath
+      tmpdir
     else
-      @tmpdir = Pathname.new(Dir.mktmpdir("#{prefix_name}-", HOMEBREW_TEMP))
+      Pathname.new(Dir.mktmpdir("#{prefix_name}-", HOMEBREW_TEMP))
     end
 
     # Make sure files inside the temporary directory have the same group as the