diff --git a/ares/configure.ac b/ares/configure.ac
index fbcb8513a9..66f44f45a7 100644
--- a/ares/configure.ac
+++ b/ares/configure.ac
@@ -239,10 +239,10 @@ if test "$curl_cv_have_def___DECC" = "yes" ||
   AC_MSG_RESULT([yes])
   dnl Select strict ANSI C compiler mode
   CFLAGS="$CFLAGS -std1"
+  dnl Select a higher warning level than default level2
+  CFLAGS="$CFLAGS -msg_enable level3"
   dnl Generate warnings for missing function prototypes
   CFLAGS="$CFLAGS -warnprotos"
-  dnl Select highest warning level
-  CFLAGS="$CFLAGS -msg_enable level6"
   dnl Change some warnings into fatal errors
   CFLAGS="$CFLAGS -msg_fatal toofewargs,toomanyargs"
 else
diff --git a/configure.ac b/configure.ac
index b3cc6c23f1..25e747d953 100644
--- a/configure.ac
+++ b/configure.ac
@@ -306,10 +306,10 @@ if test "$curl_cv_have_def___DECC" = "yes" ||
   AC_MSG_RESULT([yes])
   dnl Select strict ANSI C compiler mode
   CFLAGS="$CFLAGS -std1"
+  dnl Select a higher warning level than default level2
+  CFLAGS="$CFLAGS -msg_enable level3"
   dnl Generate warnings for missing function prototypes
   CFLAGS="$CFLAGS -warnprotos"
-  dnl Select highest warning level
-  CFLAGS="$CFLAGS -msg_enable level6"
   dnl Change some warnings into fatal errors
   CFLAGS="$CFLAGS -msg_fatal toofewargs,toomanyargs"
 else