diff --git a/ui/vnc.c b/ui/vnc.c
index 1ed360adf2..e1d6ca323e 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -879,13 +879,10 @@ static int find_and_clear_dirty_height(struct VncState *vs,
     int h;
 
     for (h = 1; h < (height - y); h++) {
-        int tmp_x;
         if (!test_bit(last_x, vs->dirty[y + h])) {
             break;
         }
-        for (tmp_x = last_x; tmp_x < x; tmp_x++) {
-            clear_bit(tmp_x, vs->dirty[y + h]);
-        }
+        bitmap_clear(vs->dirty[y + h], last_x, x - last_x);
     }
 
     return h;