diff --git a/sourcing/model.py b/sourcing/model.py
index 3ccb9a2..b9486a6 100644
--- a/sourcing/model.py
+++ b/sourcing/model.py
@@ -24,7 +24,7 @@ doc_hashids = Hashids(min_length=8)
 Base = declarative_base()
 Base.query = session.query_property()
 
-re_server_url = re.compile('^http://perma.pub/\d+/([^/]+)/([^/]+)$')
+re_server_url = re.compile(r'^http://perma.pub/\d+/([^/]+)/([^/]+)$')
 
 # list of disallowed usernames - maybe this should be in the database
 reserved_name = ['root', 'admin', 'administrator', 'support', 'info',