diff --git a/docker/auth/auth.py b/docker/auth/auth.py
index 22a9f969..c952f344 100644
--- a/docker/auth/auth.py
+++ b/docker/auth/auth.py
@@ -43,7 +43,7 @@ def expand_registry_url(hostname):
 
 def resolve_repository_name(repo_name):
     if '://' in repo_name:
-        raise ValueError('Repository name can not contain a'
+        raise ValueError('Repository name cannot contain a '
                          'scheme ({0})'.format(repo_name))
     parts = repo_name.split('/', 1)
     if not '.' in parts[0] and not ':' in parts[0] and parts[0] != 'localhost':