diff --git a/api/catalog/api/serializers/base.py b/api/catalog/api/serializers/base.py
index f07234d0b..ca54759b6 100644
--- a/api/catalog/api/serializers/base.py
+++ b/api/catalog/api/serializers/base.py
@@ -19,6 +19,6 @@ def get_url(self, *args, **kwargs):
 
         # Only rewrite URLs if a fixed scheme is provided
         if self.scheme is not None:
-            re.sub(r"^\w+://", f"{self.scheme}://", url, 1)
+            url = re.sub(r"^\w+://", f"{self.scheme}://", url, 1)
 
         return url