diff --git a/src/move.c b/src/move.c
index 8c6fbd6..20c575c 100644
--- a/src/move.c
+++ b/src/move.c
@@ -3102,7 +3102,7 @@
 
     loff.lnum = dir == FORWARD ? curwin->w_botline : curwin->w_topline - 1;
 #ifdef FEAT_DIFF
-    loff.fill = diff_check_fill(curwin, loff.lnum + dir == BACKWARD)
+    loff.fill = diff_check_fill(curwin, loff.lnum + (dir == BACKWARD))
 		- (dir == FORWARD ? curwin->w_filler_rows : curwin->w_topfill);
     loff.height = loff.fill > 0 ? 1 : plines_nofill(loff.lnum);
 #else