diff --git a/lib/src/parse.dart b/lib/src/parse.dart
index fe7f870..4c032f5 100644
--- a/lib/src/parse.dart
+++ b/lib/src/parse.dart
@@ -73,8 +73,11 @@
     }
   }
 
-  //FIXME assert stack has only one item and error message if not.
-  // Add test for this.
+  if (stack.length != 1) {
+    throw new _TemplateException(
+      "Unclosed tag: '${stack.last.name}'.",
+      templateName, source, stack.last.start);
+  }
   
   return stack.last.children;
 }
diff --git a/test/mustache_test.dart b/test/mustache_test.dart
index 8e4f686..f0782f4 100644
--- a/test/mustache_test.dart
+++ b/test/mustache_test.dart
@@ -10,6 +10,7 @@
 const BAD_TAG_NAME = 'Unless in lenient mode tags may only contain';
 const VALUE_NULL = 'Value was null or missing';
 const VALUE_MISSING = 'Value was missing';
+const UNCLOSED_TAG = 'Unclosed tag';
 
 Template parse(String source, {bool lenient: false})
   => new Template(source, lenient: lenient);
@@ -311,6 +312,12 @@
       var output = t.renderString({"section": {'var': null}});
       expect(output, equals('__'));
     });
+    
+    test('Unclosed section', () {
+      var source = r'{{#section}}foo';
+      var ex = renderFail(source, {"section": {}});
+      expectFail(ex, null, null, UNCLOSED_TAG);
+    });
 	});
 
 	group('Lenient', () {