diff --git a/fftools/cmdutils.c b/fftools/cmdutils.c
index f3c258bb99..309ec4d32f 100644
--- a/fftools/cmdutils.c
+++ b/fftools/cmdutils.c
@@ -581,7 +581,7 @@ static const AVOption *opt_find(void *obj, const char *name, const char *unit,
     return o;
 }
 
-#define FLAGS (o->type == AV_OPT_TYPE_FLAGS && (arg[0]=='-' || arg[0]=='+')) ? AV_DICT_APPEND : 0
+#define FLAGS ((o->type == AV_OPT_TYPE_FLAGS && (arg[0]=='-' || arg[0]=='+')) ? AV_DICT_APPEND : 0)
 int opt_default(void *optctx, const char *opt, const char *arg)
 {
     const AVOption *o;