diff --git a/Library/Homebrew/cmd/update.rb b/Library/Homebrew/cmd/update.rb
index f810acda0c..b21b6ec76c 100644
--- a/Library/Homebrew/cmd/update.rb
+++ b/Library/Homebrew/cmd/update.rb
@@ -76,7 +76,7 @@ class RefreshBrew
 
         @installed_formulae = HOMEBREW_CELLAR.children.
           select{ |pn| pn.directory? }.
-          map{ |pn| pn.basename.to_s }.sort
+          map{ |pn| pn.basename.to_s }.sort if HOMEBREW_CELLAR.directory?
 
         return true
       end