diff --git a/lisp/progmodes/m4-mode.el b/lisp/progmodes/m4-mode.el
index b0b0bdc..2467e8a 100644
--- a/lisp/progmodes/m4-mode.el
+++ b/lisp/progmodes/m4-mode.el
@@ -69,8 +69,7 @@ If m4 is not in your PATH, set this to an absolute file name."
     ("address@hidden" . font-lock-variable-name-face)
     ("\\$\\@" . font-lock-variable-name-face)
     ("\\$\\*" . font-lock-variable-name-face)
-    ("\\b\\(builtin\\|change\\(com\\|quote\\|word\\)\\|d\\(e\\(bug\\(file\\|mode\\)\\|cr\\|f\\(ine\\|n\\)\\)\\|iv\\(ert\\|num\\)\\|nl\\|umpdef\\)\\|e\\(rrprint\\|syscmd\\|val\\)\\|f\\(ile\\|ormat\\)\\|gnu\\|i\\(f\\(def\\|else\\)\\|n\\(c\\(lude\\|r\\)\\|d\\(ex\\|ir\\)\\)\\)\\|l\\(en\\|ine\\)\\|m\\(4\\(exit\\|wrap\\)\\|aketemp\\)\\|p\\(atsubst\\|opdef\\|ushdef\\)\\|regexp\\|s\\(hift\\|include\\|ubstr\\|ys\\(cmd\\|val\\)\\)\\|tra\\(ceo\\(ff\\|n\\)\\|nslit\\)\\|un\\(d\\(efine\\|ivert\\)\\|ix\\)\\)\\b" . font-lock-keyword-face)
-    ("\\b\\(m4_\\(builtin\\|change\\(com\\|quote\\|word\\)\\|d\\(e\\(bug\\(file\\|mode\\)\\|cr\\|f\\(ine\\|n\\)\\)\\|iv\\(ert\\|num\\)\\|nl\\|umpdef\\)\\|e\\(rrprint\\|syscmd\\|val\\)\\|f\\(ile\\|ormat\\)\\|i\\(f\\(def\\|else\\)\\|n\\(c\\(lude\\|r\\)\\|d\\(ex\\|ir\\)\\)\\)\\|l\\(en\\|ine\\)\\|m\\(4\\(_undefine\\|exit\\|wrap\\)\\|aketemp\\)\\|p\\(atsubst\\|opdef\\|ushdef\\)\\|regexp\\|s\\(hift\\|include\\|ubstr\\|ys\\(cmd\\|val\\)\\)\\|tra\\(ceo\\(ff\\|n\\)\\|nslit\\)\\|undivert\\)\\)\\b" . font-lock-keyword-face))
+    ("\\b\\(\\(m4_\\)?\\(builtin\\|change\\(com\\|quote\\|word\\)\\|d\\(e\\(bug\\(file\\|mode\\)\\|cr\\|f\\(ine\\|n\\)\\)\\|iv\\(ert\\|num\\)\\|nl\\|umpdef\\)\\|e\\(rrprint\\|syscmd\\|val\\)\\|f\\(ile\\|ormat\\)\\|i\\(f\\(def\\|else\\)\\|n\\(c\\(lude\\|r\\)\\|d\\(ex\\|ir\\)\\)\\)\\|l\\(en\\|ine\\)\\|m\\(4\\(exit\\|wrap\\)\\|aketemp\\)\\|p\\(atsubst\\|opdef\\|ushdef\\)\\|regexp\\|s\\(hift\\|include\\|ubstr\\|ys\\(cmd\\|val\\)\\)\\|tra\\(ceo\\(ff\\|n\\)\\|nslit\\)\\|un\\(d\\(efine\\|ivert\\)\\|ix\\)\\)\\)\\b" . font-lock-keyword-face))
   "Default `font-lock-keywords' for M4 mode.")
 
 (defcustom m4-mode-hook nil