diff --git a/avconv.c b/avconv.c
index 509b1dc249..876ad1996c 100644
--- a/avconv.c
+++ b/avconv.c
@@ -2434,6 +2434,7 @@ static int transcode_init(OutputFile *output_files,
 #endif
                 break;
             case AVMEDIA_TYPE_SUBTITLE:
+                codec->time_base = (AVRational){1, 1000};
                 break;
             default:
                 abort();