Index: trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java	(revision 11797)
+++ trunk/src/org/openstreetmap/josm/data/imagery/WMTSTileSource.java	(revision 11798)
@@ -408,5 +408,6 @@
         Layer layer = new Layer();
         Stack<QName> tagStack = new Stack<>();
-        List<String> supportedMimeTypes = Arrays.asList(ImageIO.getReaderMIMETypes());
+        List<String> supportedMimeTypes = new ArrayList<>(Arrays.asList(ImageIO.getReaderMIMETypes()));
+        supportedMimeTypes.add("image/jpgpng");         // used by ESRI
         Collection<String> unsupportedFormats = new ArrayList<>();