diff --git a/libavutil/opt.c b/libavutil/opt.c
index 0a909a8b22..0908751752 100644
--- a/libavutil/opt.c
+++ b/libavutil/opt.c
@@ -1752,7 +1752,7 @@ int av_opt_set_dict2(void *obj, AVDictionary **options, int search_flags)
     while ((t = av_dict_iterate(*options, t))) {
         ret = av_opt_set(obj, t->key, t->value, search_flags);
         if (ret == AVERROR_OPTION_NOT_FOUND)
-            ret = av_dict_set(&tmp, t->key, t->value, 0);
+            ret = av_dict_set(&tmp, t->key, t->value, AV_DICT_MULTIKEY);
         if (ret < 0) {
             av_log(obj, AV_LOG_ERROR, "Error setting option %s to value %s.\n", t->key, t->value);
             av_dict_free(&tmp);