Index: trunk/src/org/openstreetmap/josm/actions/MergeNodesAction.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/MergeNodesAction.java	(revision 5214)
+++ trunk/src/org/openstreetmap/josm/actions/MergeNodesAction.java	(revision 5216)
@@ -152,5 +152,5 @@
      * @return the selected target node
      */
-    public static Node selectTargetNode(List<Node> candidates) {
+    public static Node selectTargetNode(Collection<Node> candidates) {
         Node targetNode = null;
         Node lastNode = null;
@@ -241,5 +241,10 @@
 
     public static Command mergeNodes(OsmDataLayer layer, Collection<Node> nodes, Node targetNode) {
-        return mergeNodes(layer, nodes, targetNode, targetNode);
+        if (nodes == null) {
+            return null;
+        }
+        Set<Node> allNodes = new HashSet<Node>(nodes);
+        allNodes.add(targetNode);
+        return mergeNodes(layer, nodes, selectTargetNode(allNodes), targetNode);
     }