diff --git a/lcl/include/treeview.inc b/lcl/include/treeview.inc
index c775aa7296..37dfd91009 100644
--- a/lcl/include/treeview.inc
+++ b/lcl/include/treeview.inc
@@ -4003,7 +4003,7 @@ var
       tvestPlusMinus:
         begin
           // draw a plus or a minus sign
-          Rectangle(ALeft, ATop, ARight, ABottom);
+          Rectangle(ALeft, ATop, ARight+1, ABottom+1);
           MoveTo(ALeft+2,MidY);
           LineTo(ARight-2+1,MidY);
           if not CollapseSign then begin