diff --git a/libavfilter/vsrc_testsrc.c b/libavfilter/vsrc_testsrc.c
index e7d8d9ea1a..9760e5fc80 100644
--- a/libavfilter/vsrc_testsrc.c
+++ b/libavfilter/vsrc_testsrc.c
@@ -183,6 +183,7 @@ static int activate(AVFilterContext *ctx)
     if (!frame)
         return AVERROR(ENOMEM);
     frame->pts                 = test->pts;
+    frame->duration            = 1;
     frame->key_frame           = 1;
     frame->interlaced_frame    = 0;
     frame->pict_type           = AV_PICTURE_TYPE_I;