diff --git a/configure.in b/configure.in
index cfd78b9b56..e25a259269 100644
--- a/configure.in
+++ b/configure.in
@@ -262,6 +262,7 @@ AC_ARG_ENABLE(debug,
 if test "${enable_debug}" = "yes"; then
         AC_DEFINE([DEBUG],[],[Enable extra debugging.])
 	saved_CFLAGS=$CFLAGS
+	CFLAGS=
         AX_CFLAGS_WARN_ALL_ANSI
 	APR_ADDTO(SWITCH_AM_CFLAGS, $CFLAGS)
 	CFLAGS=$saved_CFLAGS