diff --git a/examples/fb/fb_main.c b/examples/fb/fb_main.c
index 9ecac2c5d..d82022010 100644
--- a/examples/fb/fb_main.c
+++ b/examples/fb/fb_main.c
@@ -177,10 +177,12 @@ static void draw_rect1(FAR struct fb_state_s *state,
   int y;
 
   row    = (FAR uint8_t *)state->fbmem + state->pinfo.stride * rect->pt1.y;
+
   startx = (rect->pt1.x >> 3);
   endx   = (rect->pt2.x >> 3);
-  lmask  = 0xff << (8 - (rect->pt1.x & 3));
-  rmask  = 0xff >> (rect->pt2.x & 3);
+
+  lmask  = 0xff << (8 - (rect->pt1.x & 7));
+  rmask  = 0xff >> (rect->pt2.x & 7);
 
   for (y = rect->pt1.y; y <= rect->pt2.y; y++)
     {