diff --git a/libavcodec/options.c b/libavcodec/options.c
index ae5e5d560b..5437770553 100644
--- a/libavcodec/options.c
+++ b/libavcodec/options.c
@@ -108,6 +108,7 @@ int avcodec_get_context_defaults3(AVCodecContext *s, const AVCodec *codec)
 
     s->time_base           = (AVRational){0,1};
     s->framerate           = (AVRational){ 0, 1 };
+    s->pkt_timebase        = (AVRational){ 0, 1 };
     s->get_buffer2         = avcodec_default_get_buffer2;
     s->get_format          = avcodec_default_get_format;
     s->execute             = avcodec_default_execute;