Fix exception
diff --git a/lib/src/lambda_context.dart b/lib/src/lambda_context.dart
index fb1fd15..fd180d1 100644
--- a/lib/src/lambda_context.dart
+++ b/lib/src/lambda_context.dart
@@ -14,7 +14,9 @@
   }
   
   _checkClosed() {
-    if (_closed) throw 'boom!'; //FIXME new TemplateException(message, template, line, column)
+    if (_closed) throw new TemplateException(
+        'LambdaContext accessed outside of callback.', 
+        _renderer._templateName, _node.line, _node.column);
   }
   
   /// Render the current section tag in the current context and return the