diff --git a/bal_addresses/subgraph.py b/bal_addresses/subgraph.py
index 4ecbcc00..01e558a6 100644
--- a/bal_addresses/subgraph.py
+++ b/bal_addresses/subgraph.py
@@ -37,7 +37,7 @@ def get_subgraph_url(self, subgraph="core") -> str:
             if chain == "zkevm":
                 return "https://subgraph.satsuma-prod.com/ab0804deff79/1xhub-ltd/aura-finance-zkevm/api"
             elif chain in ["avalanche"]:  # list of chains without an aura subgraph
-                return ""
+                return None
             else:
                 return (
                     f"https://graph.aura.finance/subgraphs/name/aura/aura-{chain}-v2-1"
diff --git a/gen_subgraph_urls.py b/gen_subgraph_urls.py
index 4cf0f656..3fc01ab0 100644
--- a/gen_subgraph_urls.py
+++ b/gen_subgraph_urls.py
@@ -13,6 +13,7 @@ def main():
         for subgraph_type in ["core", "gauges", "blocks", "aura"]:
             subgraph = Subgraph(chain)
             url = subgraph.get_subgraph_url(subgraph_type)
+            url = url if url else ""
             urls[chain].update({subgraph_type: url})
 
     # dump the collected dict to json file