diff --git a/player/video.c b/player/video.c
index 7bccdefb34..595265dc74 100644
--- a/player/video.c
+++ b/player/video.c
@@ -962,7 +962,7 @@ static void handle_display_sync_frame(struct MPContext *mpctx,
     // particular, don't attempt to change speed for them.
     if (drop) {
         drop_repeat = -av_diff / vsync; // round towards 0
-        av_diff -= drop_repeat * vsync;
+        av_diff += drop_repeat * vsync;
     }
 
     if (resample) {