diff --git a/Library/Homebrew/download_strategy.rb b/Library/Homebrew/download_strategy.rb
index 646c08c18c..cee9f9bec5 100644
--- a/Library/Homebrew/download_strategy.rb
+++ b/Library/Homebrew/download_strategy.rb
@@ -364,7 +364,7 @@ end
 
 class SubversionDownloadStrategy < VCSDownloadStrategy
   def cache_tag
-    ARGV.build_head? ? "svn-HEAD" : "svn"
+    resource.version.head? ? "svn-HEAD" : "svn"
   end
 
   def repo_valid?