Index: trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java	(revision 13746)
+++ trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java	(revision 13747)
@@ -429,5 +429,5 @@
                 cf.clear();
                 Logging.warn(new String(data, StandardCharsets.UTF_8));
-                throw new IllegalArgumentException(e);
+                throw new WMTSGetCapabilitiesException(tr("Error during parsing of WMTS Capabilities document: {1}", e.getMessage()));
             }
         }