 
     format = project['format'][zoom]
     if req.params.format != format
-        res.send(404)
+        if project['default_tile']?
+            res.contentType("png")
+            res.send project['default_tile']
+         else
+            res.send(404)
         return
 
     db = project['database'][zoom]

    current_name = current_layer['name']
    current_files = current_layer['files']
    if not current_files? or not current_name? or current_files.length == 0
        continue

    # Connection to the mbtiles db

        client.query "SELECT value FROM metadata WHERE name='format'", (error, result) ->
            if error != null
                console.log error
                return

            if result.rows.length > 0
                row = result.rows[0]
