Index: /trunk/src/org/openstreetmap/josm/gui/layer/AbstractTileSourceLayer.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/layer/AbstractTileSourceLayer.java	(revision 11544)
+++ /trunk/src/org/openstreetmap/josm/gui/layer/AbstractTileSourceLayer.java	(revision 11545)
@@ -1236,5 +1236,5 @@
         if (Main.isDebugEnabled()) {
             if (yCursor < t.getYtile()) {
-                if (t.getYtile() % 32 == 31) {
+                if (Math.abs(t.getYtile() % 32) == 31) {
                     g.fillRect(0, y - 1, mv.getWidth(), 3);
                 } else {