diff --git a/lib/src/renderer.dart b/lib/src/renderer.dart
index 86f0308..bccd7e4 100644
--- a/lib/src/renderer.dart
+++ b/lib/src/renderer.dart
@@ -139,15 +139,9 @@
       var output = value(context);
       context.close();
       if (output != null) write(output);
-    } else if (lenient) {
-      // We consider all other values as 'true' in lenient mode.
-      _renderWithValue(node, null);
     } else {
-      throw error(
-          'Invalid value type for section, '
-          'section: ${node.name}, '
-          'type: ${value.runtimeType}.',
-          node);
+      // Assume the value might have accessible member values via mirrors.
+      _renderWithValue(node, value);
     }
   }
 
@@ -249,7 +243,7 @@
     if ((field is VariableMirror) ||
         ((field is MethodMirror) && (field.isGetter))) {
       invocation = instance.getField(field.simpleName);
-    } else if ((field is MethodMirror) && (field.parameters.length == 0)) {
+    } else if ((field is MethodMirror) && (field.parameters.where((p) => !p.isOptional).length == 0)) {
       invocation = instance.invoke(field.simpleName, []);
     }
     if (invocation == null) {
diff --git a/test/mustache_specs.dart b/test/mustache_specs.dart
index 023dab1..8a25502 100644
--- a/test/mustache_specs.dart
+++ b/test/mustache_specs.dart
@@ -32,7 +32,7 @@
     if (f is File) {
       var filename = f.path;
       if (shouldRun(filename)) {
-        var text = f.readAsStringSync(encoding: UTF8);
+        var text = f.readAsStringSync(encoding: utf8);
         _defineGroupFromFile(filename, text);
       }
     }
@@ -40,8 +40,8 @@
 }
 
 _defineGroupFromFile(filename, text) {
-  var json = JSON.decode(text);
-  var tests = json['tests'];
+  var jsondata = json.decode(text);
+  var tests = jsondata['tests'];
   filename = filename.substring(filename.lastIndexOf('/') + 1);
   group("Specs of $filename", () {
 
diff --git a/test/mustache_test.dart b/test/mustache_test.dart
index 2e92d0d..f3830e9 100644
--- a/test/mustache_test.dart
+++ b/test/mustache_test.dart
@@ -15,6 +15,25 @@
 Template parse(String source, {bool lenient: false}) =>
     new Template(source, lenient: lenient);
 
+class NestedVarClass {
+  final String foo;
+  NestedVarClass(this.foo);
+}
+
+class NestedSectionClass {
+  final NestedVarClass v;
+  NestedSectionClass(this.v);
+}
+
+class SectionClass {
+  final NestedSectionClass section;
+  SectionClass(this.section);
+}
+
+class ClassWithOptionalParamMethod {
+  String myMethod([String value = 'hello']) => value;
+}
+
 main() {
   group('Basic', () {
     test('Variable', () {
@@ -55,7 +74,11 @@
     test('Invalid value', () {
       var ex = renderFail('{{#section}}_{{var}}_{{/section}}', {"section": 42});
       expect(ex is TemplateException, isTrue);
-      expect(ex.message, startsWith(BAD_VALUE_SECTION));
+      expect(ex.message, startsWith(VALUE_MISSING));
+    });
+    test('Nested classes', () {
+      var output = parse('{{#section}}_{{v.foo}}_{{/section}}').renderString(SectionClass(NestedSectionClass(NestedVarClass('hello'))));
+      expect(output, equals('_hello_'));
     });
     test('Invalid value - lenient mode', () {
       var output = parse('{{#var}}_{{var}}_{{/var}}', lenient: true)