diff --git a/cde/configure.ac b/cde/configure.ac
index b5fb19a4a..a40350e9e 100644
--- a/cde/configure.ac
+++ b/cde/configure.ac
@@ -223,7 +223,7 @@ AC_SYS_POSIX_TERMIOS
 
 AX_PTHREAD
 
-dnl AC_PROG_CC_C99, someday.
+AC_PROG_CC_C99
 
 AC_PATH_X
 AC_PATH_XTRA