diff --git a/libs/community/tests/unit_tests/load/test_serializable.py b/libs/community/tests/unit_tests/load/test_serializable.py
index 7ca4d27da91..47eff18c47b 100644
--- a/libs/community/tests/unit_tests/load/test_serializable.py
+++ b/libs/community/tests/unit_tests/load/test_serializable.py
@@ -102,6 +102,13 @@ def test_serializable_mapping() -> None:
             "modifier",
             "RemoveMessage",
         ),
+        # This is not exported from langchain, only langchain_core
+        ("langchain_core", "prompts", "content_block", "ContentBlockPromptTemplate"): (
+            "langchain_core",
+            "prompts",
+            "content_block",
+            "ContentBlockPromptTemplate",
+        ),
     }
     serializable_modules = import_all_modules("langchain")
 
diff --git a/libs/core/langchain_core/load/mapping.py b/libs/core/langchain_core/load/mapping.py
index 4013170fdb3..9b412ead253 100644
--- a/libs/core/langchain_core/load/mapping.py
+++ b/libs/core/langchain_core/load/mapping.py
@@ -147,7 +147,7 @@ SERIALIZABLE_MAPPING: Dict[Tuple[str, ...], Tuple[str, ...]] = {
         "image",
         "ImagePromptTemplate",
     ),
-    ("langchain", "prompts", "content_block", "ContentBlockPromptTemplate"): (
+    ("langchain_core", "prompts", "content_block", "ContentBlockPromptTemplate"): (
         "langchain_core",
         "prompts",
         "content_block",
diff --git a/libs/core/langchain_core/prompts/content_block.py b/libs/core/langchain_core/prompts/content_block.py
index e89d346a753..8210b6ec71f 100644
--- a/libs/core/langchain_core/prompts/content_block.py
+++ b/libs/core/langchain_core/prompts/content_block.py
@@ -46,7 +46,7 @@ class ContentBlockPromptTemplate(BasePromptTemplate[Dict[str, Any]]):
     @classmethod
     def get_lc_namespace(cls) -> List[str]:
         """Get the namespace of the langchain object."""
-        return ["langchain", "prompts", "content_block"]
+        return ["langchain_core", "prompts", "content_block"]
 
     def format(self, **kwargs: Any) -> Dict[str, Any]:
         """Format the prompt with the inputs.