diff --git a/libavutil/downmix_info.c b/libavutil/downmix_info.c
index c634c6a79f..feaee28493 100644
--- a/libavutil/downmix_info.c
+++ b/libavutil/downmix_info.c
@@ -27,9 +27,11 @@ AVDownmixInfo *av_downmix_info_update_side_data(AVFrame *frame)
 
     side_data = av_frame_get_side_data(frame, AV_FRAME_DATA_DOWNMIX_INFO);
 
-    if (!side_data)
+    if (!side_data) {
         side_data = av_frame_new_side_data(frame, AV_FRAME_DATA_DOWNMIX_INFO,
                                            sizeof(AVDownmixInfo));
+        memset(side_data->data, 0, sizeof(AVDownmixInfo));
+    }
 
     if (!side_data)
         return NULL;