diff --git a/hexlib/env.py b/hexlib/env.py
index 90da20a..dacdce3 100644
--- a/hexlib/env.py
+++ b/hexlib/env.py
@@ -18,5 +18,5 @@ def get_web():
         rps=os.environ.get("RPS", 1),
         logger=stdout_logger,
         cookie_file=os.environ.get("COOKIE_FILE", None),
-        retry_codes=set(int(x) for x in os.environ.get("RETRY_CODES", "").split(","))
+        retry_codes=set(int(x) if x else None for x in os.environ.get("RETRY_CODES", "").split(","))
     )