diff --git a/lisp/frame.el b/lisp/frame.el
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -38,7 +38,7 @@ window-system
   ;; so just use it, and anyway `eql' isn't very useful on cons cells.
   `(window-system ,(if (consp value) value `(eql ',value))))
 
-(cl-defmethod frame-creation-function (params &context (window-system nil))
+(cl-defmethod frame-creation-function (params &context (window-system (eql 'nil)))
   ;; It's tempting to get rid of tty-create-frame-with-faces and turn it into
   ;; this method (i.e. move this method to faces.el), but faces.el is loaded
   ;; much earlier from loadup.el (before cl-generic and even before