diff --git a/video/out/vo_drm.c b/video/out/vo_drm.c
index 8262fce88d..e66058657b 100644
--- a/video/out/vo_drm.c
+++ b/video/out/vo_drm.c
@@ -443,6 +443,8 @@ static int preinit(struct vo *vo)
         goto err;
     }
 
+    vo->monitor_par = 1 / vo->opts->monitor_pixel_aspect;
+
     return 0;
 
 err: