Index: applications/editors/josm/plugins/wmsplugin/src/wmsplugin/GeorefImage.java
===================================================================
--- applications/editors/josm/plugins/wmsplugin/src/wmsplugin/GeorefImage.java	(revision 13652)
+++ applications/editors/josm/plugins/wmsplugin/src/wmsplugin/GeorefImage.java	(revision 13654)
@@ -23,5 +23,5 @@
 public class GeorefImage implements Serializable {
     public BufferedImage image = null;
-    private BufferedImage reImg = null;
+    private Image reImg = null;
     private Dimension reImgHash = new Dimension(0, 0);
     public EastNorth min, max;
@@ -121,3 +121,7 @@
 		return out_img;
 	}
+    
+    public void flushedResizedCachedInstance() {
+        reImg = null;
+    }
 }
Index: applications/editors/josm/plugins/wmsplugin/src/wmsplugin/WMSLayer.java
===================================================================
--- applications/editors/josm/plugins/wmsplugin/src/wmsplugin/WMSLayer.java	(revision 13652)
+++ applications/editors/josm/plugins/wmsplugin/src/wmsplugin/WMSLayer.java	(revision 13654)
@@ -248,5 +248,13 @@
             boolean alphaChannel = checkbox.isSelected();
             Main.pref.put("wmsplugin.alpha_channel", alphaChannel);
-            Main.map.repaint();
+            
+            // clear all resized cached instances and repaint the layer
+            for (int x = 0; x < dax; ++x) {
+                for (int y = 0; y < day; ++y) {
+                    GeorefImage img = images[modulo(x, dax)][modulo(y, day)];
+                    img.flushedResizedCachedInstance();
+                }
+            }
+            mv.repaint();
         }
     }