diff --git a/libavformat/mxfenc.c b/libavformat/mxfenc.c
index 4ac6a2d715..57be9e6ef6 100644
--- a/libavformat/mxfenc.c
+++ b/libavformat/mxfenc.c
@@ -2894,8 +2894,12 @@ static int mxf_init(AVFormatContext *s)
 
         if (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
             const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(st->codecpar->format);
-            // TODO: should be avg_frame_rate
-            AVRational tbc = st->time_base;
+            AVRational tbc = (AVRational){ 0, 0 };
+            if (st->avg_frame_rate.num > 0 && st->avg_frame_rate.den > 0)
+                tbc = av_inv_q(st->avg_frame_rate);
+            else if (st->r_frame_rate.num > 0 && st->r_frame_rate.den > 0)
+                tbc = av_inv_q(st->r_frame_rate);
+
             // Default component depth to 8
             sc->component_depth = 8;
             sc->h_chroma_sub_sample = 2;
diff --git a/tests/ref/fate/time_base b/tests/ref/fate/time_base
index fd6cac53fc..23875d1fb8 100644
--- a/tests/ref/fate/time_base
+++ b/tests/ref/fate/time_base
@@ -1 +1 @@
-d408aba82d62a90ed7f46a1999b014f1
+b28d4ca13029fdc80a114b56467be9d7