diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index 0a4f74e4ca..32492c6be9 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -108,7 +108,7 @@ class BuildError < Homebrew::InstallationError
     @command = cmd
     @env = ENV.to_hash
     @exit_status = es.exitstatus rescue 1
-    args = args.map{ |arg| arg.gsub " ", "\\ " }.join(" ")
+    args = args.map{ |arg| arg.to_s.gsub " ", "\\ " }.join(" ")
     super formula, "Failed executing: #{command} #{args}"
   end