diff --git a/configure.ac b/configure.ac
index 24eb24f..3a0ef16 100644
--- a/configure.ac
+++ b/configure.ac
@@ -9,8 +9,8 @@ AC_CONFIG_MACRO_DIR([m4])
 
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
-AC_SUBST([USER_CFLAGS], "-O2 $CFLAGS")
-CFLAGS="$CFLAGS -Wall -std=gnu99 -g"
+AC_SUBST([USER_CFLAGS], "$CFLAGS")
+CFLAGS="-Wall -std=gnu99 -g -O2"
 
 case $host_os in
 	*darwin*)