Index: trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 11763)
+++ trunk/src/org/openstreetmap/josm/gui/dialogs/properties/PropertiesDialog.java	(revision 11764)
@@ -990,5 +990,6 @@
                     nextKeyIndex++;
                 }
-                nextKey = editHelper.getDataKey(nextKeyIndex);
+                // We use unfiltered indexes here. So don't use getDataKey()
+                nextKey = (String) tagData.getValueAt(nextKeyIndex, 0);
             }