diff --git a/libs/core/langchain_core/messages/base.py b/libs/core/langchain_core/messages/base.py
index 9eab1ed431a..0c59f77e06e 100644
--- a/libs/core/langchain_core/messages/base.py
+++ b/libs/core/langchain_core/messages/base.py
@@ -198,6 +198,7 @@ class BaseMessageChunk(BaseMessage):
 
             return self.__class__(  # type: ignore[call-arg]
                 id=self.id,
+                type=self.type,
                 content=merge_content(self.content, other.content),
                 additional_kwargs=merge_dicts(
                     self.additional_kwargs, other.additional_kwargs