diff --git a/coverage/fuel3.html b/coverage/fuel3.html
index 86e0424..aa8642e 100644
--- a/coverage/fuel3.html
+++ b/coverage/fuel3.html
@@ -95,12 +95,14 @@
 </script>
 <script type="text/javascript">
     const ort = new ol.layer.Tile({
-        source: new ol.source.OSM({
-            "url" : "http://tiles.wmflabs.org/bw-mapnik/" + "{z}/{x}/{y}.png"
-        }),
+        source: new ol.source.OSM(),
         title: "OpenStreetMap gray",
         visible: true
     });
+    
+    ort.on('postcompose', function(event) {
+        greyscale(event.context);
+    });
 
     const fuel0 = new ol.layer.VectorTile({
         source: new ol.source.VectorTile({