diff --git a/libs/core/langchain_core/messages/content_blocks.py b/libs/core/langchain_core/messages/content_blocks.py
index a2efd0fef9c..e459915c75d 100644
--- a/libs/core/langchain_core/messages/content_blocks.py
+++ b/libs/core/langchain_core/messages/content_blocks.py
@@ -706,6 +706,7 @@ ToolContentBlock = Union[
 ContentBlock = Union[
     TextContentBlock,
     ToolCall,
+    InvalidToolCall,
     ReasoningContentBlock,
     NonStandardContentBlock,
     DataContentBlock,