Index: /trunk/src/org/openstreetmap/josm/io/Capabilities.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/io/Capabilities.java	(revision 12199)
+++ /trunk/src/org/openstreetmap/josm/io/Capabilities.java	(revision 12200)
@@ -153,6 +153,9 @@
      */
     public boolean supportsVersion(String version) {
-        return get("version", "minimum").compareTo(version) <= 0
-            && get("version", "maximum").compareTo(version) >= 0;
+        String min = get("version", "minimum");
+        String max = get("version", "maximum");
+        return min != null && max != null
+            && min.compareTo(version) <= 0
+            && max.compareTo(version) >= 0;
     }