diff --git a/libs/core/langchain_core/messages/ai.py b/libs/core/langchain_core/messages/ai.py
index c81187dc3f6..27ae49dca9f 100644
--- a/libs/core/langchain_core/messages/ai.py
+++ b/libs/core/langchain_core/messages/ai.py
@@ -358,7 +358,10 @@ class AIMessageChunk(AIMessage, BaseMessageChunk):
 
         for chunk in self.tool_call_chunks:
             try:
-                args_ = parse_partial_json(chunk["args"]) if chunk["args"] != "" else {}  # type: ignore[arg-type]
+                if chunk["args"] is not None and chunk["args"] != "":
+                    args_ = parse_partial_json(chunk["args"])
+                else:
+                    args_ = {}
                 if isinstance(args_, dict):
                     tool_calls.append(
                         create_tool_call(
diff --git a/libs/core/tests/unit_tests/test_messages.py b/libs/core/tests/unit_tests/test_messages.py
index 0656a2f2e97..807f52ae10d 100644
--- a/libs/core/tests/unit_tests/test_messages.py
+++ b/libs/core/tests/unit_tests/test_messages.py
@@ -455,9 +455,9 @@ def test_message_chunk_to_message() -> None:
         tool_calls=[
             create_tool_call(name="tool1", args={"a": 1}, id="1"),
             create_tool_call(name="tool2", args={}, id="2"),
+            create_tool_call(name="tool3", args={}, id="3"),
         ],
         invalid_tool_calls=[
-            create_invalid_tool_call(name="tool3", args=None, id="3", error=None),
             create_invalid_tool_call(name="tool4", args="abc", id="4", error=None),
         ],
     )