diff --git a/usr.bin/m4/gnum4.c b/usr.bin/m4/gnum4.c
index 782090d3a0ed..b265b8d478e9 100644
--- a/usr.bin/m4/gnum4.c
+++ b/usr.bin/m4/gnum4.c
@@ -25,6 +25,9 @@
  * SUCH DAMAGE.
  */
 
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
 /* 
  * functions needed to support gnu-m4 extensions, including a fake freezing
  */