--- a/src/signs.cpp	Sat May 26 10:40:34 2007 +0000
+++ b/src/signs.cpp	Sat May 26 12:19:54 2007 +0000
@@ -64,11 +64,14 @@
  */
 static void MarkSignDirty(Sign *si)
 {
+	/* We use ZOOM_LVL_MAX here, as every viewport can have an other zoom,
+		*  and there is no way for us to know which is the biggest. So make the
+		*  biggest area dirty, and we are safe for sure. */
 	MarkAllViewportsDirty(
 		si->sign.left - 6,
 		si->sign.top  - 3,
-		si->sign.left + ScaleByZoom(si->sign.width_1 + 12, _cur_dpi->zoom),
-		si->sign.top  + ScaleByZoom(12, _cur_dpi->zoom));
+		si->sign.left + ScaleByZoom(si->sign.width_1 + 12, ZOOM_LVL_MAX),
+		si->sign.top  + ScaleByZoom(12, ZOOM_LVL_MAX));
 }
 
 /**