Index: trunk/src/org/openstreetmap/josm/io/session/SessionWriter.java
===================================================================
--- trunk/src/org/openstreetmap/josm/io/session/SessionWriter.java	(revision 8597)
+++ trunk/src/org/openstreetmap/josm/io/session/SessionWriter.java	(revision 8620)
@@ -38,4 +38,5 @@
 import org.openstreetmap.josm.gui.layer.TMSLayer;
 import org.openstreetmap.josm.gui.layer.WMSLayer;
+import org.openstreetmap.josm.gui.layer.WMTSLayer;
 import org.openstreetmap.josm.gui.layer.geoimage.GeoImageLayer;
 import org.openstreetmap.josm.gui.layer.markerlayer.MarkerLayer;
@@ -54,4 +55,5 @@
         registerSessionLayerExporter(TMSLayer.class , ImagerySessionExporter.class);
         registerSessionLayerExporter(WMSLayer.class , ImagerySessionExporter.class);
+        registerSessionLayerExporter(WMTSLayer.class , ImagerySessionExporter.class);
         registerSessionLayerExporter(GpxLayer.class , GpxTracksSessionExporter.class);
         registerSessionLayerExporter(GeoImageLayer.class , GeoImageSessionExporter.class);