Index: /applications/editors/josm/plugins/slippymap/src/org/openstreetmap/josm/plugins/slippymap/SlippyMapLayer.java
===================================================================
--- /applications/editors/josm/plugins/slippymap/src/org/openstreetmap/josm/plugins/slippymap/SlippyMapLayer.java	(revision 18730)
+++ /applications/editors/josm/plugins/slippymap/src/org/openstreetmap/josm/plugins/slippymap/SlippyMapLayer.java	(revision 18731)
@@ -216,4 +216,8 @@
                 new AbstractAction(tr("Snap to tile size")) {
                     public void actionPerformed(ActionEvent ae) {
+                        if (lastImageScale == null) {
+                            out("please wait for a tile to be loaded before snapping");
+                            return;
+                        }
                         double new_factor = Math.sqrt(lastImageScale);
                         if (debug)
@@ -628,6 +632,5 @@
                 continue;
             drawImageInside(g, img, sourceRect, borderRect);
-            if (autoZoomEnabled() &&
-                !imageScaleRecorded && zoom == currentZoomLevel) {
+            if (!imageScaleRecorded && zoom == currentZoomLevel) {
                 lastImageScale = new Double(getImageScaling(img, sourceRect));
                 imageScaleRecorded = true;