diff --git a/libavformat/cdg.c b/libavformat/cdg.c
index f0c14a6366..baf37d4c6a 100644
--- a/libavformat/cdg.c
+++ b/libavformat/cdg.c
@@ -46,10 +46,11 @@ static int read_header(AVFormatContext *s)
     avpriv_set_pts_info(vst, 32, 1, 300);
 
     ret = avio_size(s->pb);
-    if (ret < 0)
-        return ret;
+    if (ret < 0) {
+        av_log(s, AV_LOG_WARNING, "Cannot calculate duration as file size cannot be determined\n");
+    } else
+        vst->duration = (ret * vst->time_base.den) / (CDG_PACKET_SIZE * 300);
 
-    vst->duration = (ret * vst->time_base.den) / (CDG_PACKET_SIZE * 300);
     return 0;
 }