diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 9c88c8d710..b12b39f990 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -233,6 +233,7 @@ protected
         wr.close
         out << rd.read until rd.eof?
       end
+      Process.wait
       unless $?.success?
         puts out
         raise