diff --git a/api/core/datasource/utils/message_transformer.py b/api/core/datasource/utils/message_transformer.py
index 04f15dee31..c012e128f4 100644
--- a/api/core/datasource/utils/message_transformer.py
+++ b/api/core/datasource/utils/message_transformer.py
@@ -71,8 +71,8 @@ class DatasourceFileMessageTransformer:
                 if not isinstance(message.message, DatasourceMessage.BlobMessage):
                     raise ValueError("unexpected message type")
 
-                # FIXME: should do a type check here.
-                assert isinstance(message.message.blob, bytes)
+                if not isinstance(message.message.blob, bytes):
+                    raise TypeError(f"Expected blob to be bytes, got {type(message.message.blob).__name__}")
                 tool_file_manager = ToolFileManager()
                 blob_tool_file: ToolFile | None = tool_file_manager.create_file_by_raw(
                     user_id=user_id,
diff --git a/api/core/tools/utils/message_transformer.py b/api/core/tools/utils/message_transformer.py
index bb5b3ba76e..2264981abd 100644
--- a/api/core/tools/utils/message_transformer.py
+++ b/api/core/tools/utils/message_transformer.py
@@ -118,7 +118,8 @@ class ToolFileMessageTransformer:
                 if not isinstance(message.message, ToolInvokeMessage.BlobMessage):
                     raise ValueError("unexpected message type")
 
-                assert isinstance(message.message.blob, bytes)
+                if not isinstance(message.message.blob, bytes):
+                    raise TypeError(f"Expected blob to be bytes, got {type(message.message.blob).__name__}")
                 tool_file_manager = ToolFileManager()
                 tool_file = tool_file_manager.create_file_by_raw(
                     user_id=user_id,