diff --git a/api/core/file/file_manager.py b/api/core/file/file_manager.py
index eb260a8f84..0b34349ba5 100644
--- a/api/core/file/file_manager.py
+++ b/api/core/file/file_manager.py
@@ -74,6 +74,8 @@ def to_prompt_message_content(
                 data = _to_url(f)
             else:
                 data = _to_base64_data_string(f)
+            if f.extension is None:
+                raise ValueError("Missing file extension")
             return VideoPromptMessageContent(data=data, format=f.extension.lstrip("."))
         case _:
             raise ValueError("file type f.type is not supported")
diff --git a/api/tests/unit_tests/core/workflow/nodes/llm/test_node.py b/api/tests/unit_tests/core/workflow/nodes/llm/test_node.py
index 6ec219aa8d..36c3042ff6 100644
--- a/api/tests/unit_tests/core/workflow/nodes/llm/test_node.py
+++ b/api/tests/unit_tests/core/workflow/nodes/llm/test_node.py
@@ -248,6 +248,7 @@ def test_fetch_prompt_messages__vison_disabled(faker, llm_node, model_config):
 def test_fetch_prompt_messages__basic(faker, llm_node, model_config):
     # Setup dify config
     dify_config.MULTIMODAL_SEND_IMAGE_FORMAT = "url"
+    dify_config.MULTIMODAL_SEND_VIDEO_FORMAT = "url"
 
     # Generate fake values for prompt template
     fake_assistant_prompt = faker.sentence()
@@ -443,9 +444,10 @@ def test_fetch_prompt_messages__basic(faker, llm_node, model_config):
                 "input.image": File(
                     tenant_id="test",
                     type=FileType.VIDEO,
-                    filename="test1.jpg",
+                    filename="test1.mp4",
                     transfer_method=FileTransferMethod.REMOTE_URL,
                     remote_url=fake_remote_url,
+                    extension="mp4",
                 )
             },
         ),