diff --git a/aclocal.m4 b/aclocal.m4
index 2158097046..38c74b2129 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -613,7 +613,7 @@ AC_DEFUN([FP_SET_CFLAGS_C99],
CPPFLAGS="$$3"
unset ac_cv_prog_cc_c99
dnl perform detection
- _AC_PROG_CC_C99
+ AC_PROG_CC_C99
fp_cc_c99="$ac_cv_prog_cc_c99"
case "x$ac_cv_prog_cc_c99" in
x) ;; # noop
