Index: trunk/src/org/openstreetmap/josm/io/OsmApi.java
===================================================================
--- trunk/src/org/openstreetmap/josm/io/OsmApi.java	(revision 1866)
+++ trunk/src/org/openstreetmap/josm/io/OsmApi.java	(revision 1867)
@@ -468,5 +468,9 @@
 
                 if (retCode != 200)
-                    throw new OsmApiException(retCode,errorHeader.trim(),responseBody.toString().trim());
+                    throw new OsmApiException(
+                            retCode,
+                            errorHeader == null? null : errorHeader.trim(),
+                                    responseBody == null ? null : responseBody.toString().trim()
+                    );
 
                 return responseBody.toString();