diff --git a/configure.in b/configure.in
index 07996c9e..60574270 100644
--- a/configure.in
+++ b/configure.in
@@ -6,8 +6,10 @@ dnl
 dnl C Compiler
 dnl
 
+if test x$CFLAGS = x; then
+	AC_SUBST(CFLAGS, [ ])
+fi
 AC_PROG_CC
-AC_SUBST(CFLAGS, [ ])
 AC_PROG_LIBTOOL
 PKG_PROG_PKG_CONFIG([0.17.2])