diff --git a/configure.ac b/configure.ac
index 052c39cf47c..119323d1692 100644
--- a/configure.ac
+++ b/configure.ac
@@ -183,8 +183,7 @@ AC_PROG_CC([cc gcc])
 PHP_DETECT_ICC
 PHP_DETECT_SUNCC
 AC_PROG_CC_C_O
-dnl Change to AC_PROG_CC_STDC when we start requiring a post-2.13 autoconf
-dnl AC_PROG_CC_STDC
+AC_PROG_CC_C99
 AC_PROG_CPP
 AC_USE_SYSTEM_EXTENSIONS
 AC_PROG_LN_S