Index: test/filterClasses.js
===================================================================
--- a/test/filterClasses.js
+++ b/test/filterClasses.js
@@ -178,23 +178,23 @@
   test.equal(result.sort().join("\n"), expected.sort().join("\n"), text);
 
   // Test round-trip
   let filter2;
   let buffer = [];
   filter.serialize(buffer);
   if (buffer.length)
   {
-    let map = Object.create(null);
+    let map = new Map();
     for (let line of buffer.slice(1))
     {
       if (/(.*?)=(.*)/.test(line))
-        map[RegExp.$1] = RegExp.$2;
+        map.set(RegExp.$1, RegExp.$2);
     }
-    filter2 = Filter.fromObject(map);
+    filter2 = Filter.fromMap(map);
   }
   else
     filter2 = Filter.fromText(filter.text);
 
   test.equal(serializeFilter(filter).join("\n"), serializeFilter(filter2).join("\n"), text + " deserialization");
 }
 
 exports.testFilterClassDefinitions = function(test)