When html file is opened with the default html major mode mhtml-mode the minibuffer will show this error message: Eval error in the ‘c-lang-defvar’ or ‘c-lang-setvar’ for ‘font-lock-comment-end-skip’ (fallback source eval - js-mode compiled with CC Mode 5.34 but loaded with 5.34.1): (error "‘c-font-lock-comment-end-skip’ got no (prior) value in js-mode (might be a cyclic reference)") [2 times] mhtml-mode I think this can be seen with any html file but I have attached a simple "test.html" for testing. emacs -Q test.html