diff --git a/app/main.py b/app/main.py
index ea26f64..4b04b69 100644
--- a/app/main.py
+++ b/app/main.py
@@ -52,8 +52,8 @@ LEASE_EXPIRE_DELTA = relativedelta(days=int(getenv('LEASE_EXPIRE_DAYS', 90)))
 
 DLS_URL = str(getenv('DLS_URL', 'localhost'))
 DLS_PORT = int(getenv('DLS_PORT', '443'))
-SITE_KEY_XID = getenv('SITE_KEY_XID', '00000000-0000-0000-0000-000000000000')
-INSTANCE_REF = '00000000-0000-0000-0000-000000000000'
+SITE_KEY_XID = str(getenv('SITE_KEY_XID', '00000000-0000-0000-0000-000000000000'))
+INSTANCE_REF = str(getenv('INSTANCE_REF', '00000000-0000-0000-0000-000000000000'))
 INSTANCE_KEY_RSA = load_key(join(dirname(__file__), 'cert/instance.private.pem'))
 INSTANCE_KEY_PUB = load_key(join(dirname(__file__), 'cert/instance.public.pem'))