diff --git a/Library/Homebrew/download_strategy.rb b/Library/Homebrew/download_strategy.rb
index 03d591929c..9548a268b7 100644
--- a/Library/Homebrew/download_strategy.rb
+++ b/Library/Homebrew/download_strategy.rb
@@ -216,7 +216,7 @@ class SubversionDownloadStrategy < AbstractDownloadStrategy
       @co = HOMEBREW_CACHE + "#{name}--svn"
     end
 
-    @co + "-HEAD" if ARGV.build_head?
+    @co += "-HEAD" if ARGV.build_head?
   end
 
   def cached_location