diff --git a/files/acme_renew_cert.py b/files/acme_renew_cert.py
index b9eecd6..571db39 100755
--- a/files/acme_renew_cert.py
+++ b/files/acme_renew_cert.py
@@ -345,6 +345,19 @@ def main():
         logging.error(f"Unable to load config file: {e}")
         return 1
 
+    if isinstance(config["domains"], list):
+        domains = {domain.name: domain for domain in config["domains"]}
+        if len(domains) != len(config["domains"]):
+            domain_uniques = set()
+            domain_duplicates = set()
+            for domain in config["domains"]:
+                if domain.name not in domain_uniques:
+                    domain_uniques.add(domain.name)
+                else:
+                    domain_duplicates.add(domain.name)
+            logging.error(f"Duplicate domain name(s) found: {domain_uniques}")
+            return 2
+
     try:
         domains_to_renew = []
         for domain_name, domain_details in config["domains"].items():
@@ -385,7 +398,7 @@ def main():
             domain.renew_cert(challenge, force=args.force)
     except Exception as e:
         logging.exception(e)
-        return 2
+        return 3
 
 
 if __name__ == '__main__':