Index: trunk/src/org/openstreetmap/josm/gui/layer/geoimage/ImageViewerDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/layer/geoimage/ImageViewerDialog.java	(revision 7618)
+++ trunk/src/org/openstreetmap/josm/gui/layer/geoimage/ImageViewerDialog.java	(revision 7619)
@@ -364,5 +364,7 @@
     @Override
     public void activeLayerChange(Layer oldLayer, Layer newLayer) {
-        // Ignored
+        if (currentLayer == null && newLayer instanceof GeoImageLayer) {
+            ((GeoImageLayer)newLayer).showFirstPhoto();
+        }
     }
 
@@ -378,4 +380,8 @@
             showImage(null, null);
         }
+        // Check buttons state in case of layer merging
+        if (currentLayer != null && oldLayer instanceof GeoImageLayer) {
+            currentLayer.checkPreviousNextButtons();
+        }
     }
 }