diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index 16ed0a9a8c..cadebe8ce5 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -61,7 +61,7 @@ module Homebrew extend self
   private
 
   def tap_args
-    ARGV.first =~ %r{^(\w+)/(homebrew-)?(\w+)$}
+    ARGV.first =~ %r{^(\S+)/(homebrew-)?(\w+)$}
     raise "Invalid usage" unless $1 and $3
     [$1, $3]
   end