diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index 7e6103a390..6f2fb849c1 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -266,7 +266,7 @@ class BuildError < RuntimeError
     end
 
     require "diagnostic"
-    unsupported_osx = Diagnostic::Checks.new.check_for_unsupported_osx
+    unsupported_osx = Homebrew::Diagnostic::Checks.new.check_for_unsupported_osx
     opoo unsupported_osx if unsupported_osx
   end
 end