diff --git a/gitk b/gitk
index e1848cd5284..f88c06e565c 100755
--- a/gitk
+++ b/gitk
@@ -2700,7 +2700,7 @@ proc getmergediffline {mdf id np} {
 	incr nextupdate 100
 	fileevent $mdf readable {}
 	update
-	fileevent $mdf readable [list getmergediffline $mdf $id]
+	fileevent $mdf readable [list getmergediffline $mdf $id $np]
     }
 }