diff --git a/libavfilter/af_channelmap.c b/libavfilter/af_channelmap.c
index 810615fedc..50e961cd4b 100644
--- a/libavfilter/af_channelmap.c
+++ b/libavfilter/af_channelmap.c
@@ -271,6 +271,12 @@ static av_cold int channelmap_init(AVFilterContext *ctx)
         }
         s->output_layout = fmt;
     }
+    if (!s->output_layout) {
+        av_log(ctx, AV_LOG_ERROR, "Output channel layout is not set and "
+               "cannot be guessed from the maps.\n");
+        return AVERROR(EINVAL);
+    }
+
     ff_add_channel_layout(&s->channel_layouts, s->output_layout);
 
     if (mode == MAP_PAIR_INT_STR || mode == MAP_PAIR_STR_STR) {
diff --git a/libavfilter/graphparser.c b/libavfilter/graphparser.c
index 3718d09c99..9241cf3bf2 100644
--- a/libavfilter/graphparser.c
+++ b/libavfilter/graphparser.c
@@ -126,7 +126,10 @@ static int create_filter(AVFilterContext **filt_ctx, AVFilterGraph *ctx, int ind
     ret = avfilter_init_str(*filt_ctx, args);
     if (ret < 0) {
         av_log(log_ctx, AV_LOG_ERROR,
-               "Error initializing filter '%s' with args '%s'\n", filt_name, args);
+               "Error initializing filter '%s'", filt_name);
+        if (args)
+            av_log(log_ctx, AV_LOG_ERROR, " with args '%s'", args);
+        av_log(log_ctx, AV_LOG_ERROR, "\n");
         return ret;
     }