diff --git a/libavfilter/af_channelmap.c b/libavfilter/af_channelmap.c
index 09d2de21f6..398b3dd0e5 100644
--- a/libavfilter/af_channelmap.c
+++ b/libavfilter/af_channelmap.c
@@ -196,7 +196,7 @@ static av_cold int channelmap_init(AVFilterContext *ctx, const char *args)
             s->map[i].out_channel_idx = i;
             break;
         case MAP_ONE_STR:
-            if (!get_channel(&mapping, &in_ch, ',')) {
+            if (get_channel(&mapping, &in_ch, ',') < 0) {
                 av_log(ctx, AV_LOG_ERROR, err);
                 ret = AVERROR(EINVAL);
                 goto fail;