For each property should work with Map instances.

runtime/helpers.js

@@ -171,6 +171,10 @@ exports.fp = function forEachPropertyHelper(o, func) {
         for (var i=0; i<o.length; i++) {
             func(i, o[i]);
         }
+    } else if (typeof Map && o instanceof Map) {
+        o.forEach(function(v, k) {
+            func(k, v);
+        });
     } else {
         for (var k in o) {
             if (o.hasOwnProperty(k)) {

test/autotests/render/for-props-map/expected.html

@@ -0,0 +1 @@
+[foo=low][bar=high]

test/autotests/render/for-props-map/template.marko

@@ -0,0 +1,3 @@
+<for(name,value in data.myMap)>
+    [${name}=${value}]
+</for>

test/autotests/render/for-props-map/test.js

@@ -0,0 +1,10 @@
+'use strict';
+
+const myMap = new Map();
+
+myMap.set('foo', 'low');
+myMap.set('bar', 'high');
+
+exports.templateData = {
+    myMap: myMap
+};