diff --git a/data/registry_model/shared.py b/data/registry_model/shared.py
index 509a0bcc5..ae0155f63 100644
--- a/data/registry_model/shared.py
+++ b/data/registry_model/shared.py
@@ -453,6 +453,8 @@ class SharedModel:
     return None
 
   def _lookup_repo_storages_by_content_checksum(self, repo, checksums, by_manifest=False):
+    checksums = set(checksums)
+
     # Load any shared storages first.
     extra_storages = []
     for checksum in list(checksums):