diff --git a/ffplayout.yml b/ffplayout.yml
index dae73992..ce18c36f 100644
--- a/ffplayout.yml
+++ b/ffplayout.yml
@@ -117,7 +117,7 @@ out:
     mode: 'stream'
     preview: False
     preview_param: >-
-        -s 512+288
+        -s 512x288
         -c:v libx264
         -crf 24
         -x264-params keyint=50:min-keyint=25:scenecut=-1