1 files changed, 1 insertions, 1 deletions
diff --git a/nodes.py b/nodes.py
index 75cefb6..96f3190 100644
--- a/nodes.py
+++ b/nodes.py
@@ -97,5 +97,5 @@ class SequenceNode(CollectionNode):
 
 
 class MappingNode(CollectionNode):
-    __slots__ = ()
+    __slots__ = ('merge', )
     id = 'mapping'