diff --git a/src/refiners/conversion/utils.py b/src/refiners/conversion/utils.py
index 86352e37..49c4e2e9 100644
--- a/src/refiners/conversion/utils.py
+++ b/src/refiners/conversion/utils.py
@@ -63,8 +63,8 @@ def __init__(
         self,
         repo_id: str,
         filename: str,
-        expected_sha256: str,
         revision: str = "main",
+        expected_sha256: str | None = None,
         download_url: str | None = None,
     ) -> None:
         """Initialize the HubPath.
@@ -79,7 +79,7 @@ def __init__(
         self.repo_id = repo_id
         self.filename = filename
         self.revision = revision
-        self.expected_sha256 = expected_sha256.lower()
+        self.expected_sha256 = expected_sha256.lower() if expected_sha256 is not None else None
         self.override_download_url = download_url
 
     @staticmethod
@@ -135,6 +135,7 @@ def local_hash(self) -> str:
 
     def check_local_hash(self) -> bool:
         """Check if the sha256 hash of the file in the local hub is correct."""
+        assert self.expected_sha256 is not None, f"{self.repo_id}/{self.filename} has no expected sha256 hash"
         if self.expected_sha256 != self.local_hash:
             logging.warning(f"{self.local_path} local sha256 mismatch, {self.local_hash} != {self.expected_sha256}")
             return False
@@ -144,6 +145,7 @@ def check_local_hash(self) -> bool:
 
     def check_remote_hash(self) -> bool:
         """Check if the sha256 hash of the file on the hf hub is correct."""
+        assert self.expected_sha256 is not None, f"{self.repo_id}/{self.filename} has no expected sha256 hash"
         if self.expected_sha256 != self.hf_sha256_hash:
             logging.warning(
                 f"{self.local_path} remote sha256 mismatch, {self.hf_sha256_hash} != {self.expected_sha256}"