diff --git a/util/tufmetadata/api.py b/util/tufmetadata/api.py
index 1ef607c6b..f3520ca4b 100644
--- a/util/tufmetadata/api.py
+++ b/util/tufmetadata/api.py
@@ -1,5 +1,6 @@
 import logging
 from urlparse import urljoin
+from posixpath import join
 
 import requests
 
@@ -107,7 +108,7 @@ class TUFMetadataAPI(object):
     return True
   
   def _gun(self, namespace, repository):
-    return urljoin(self._gun_prefix, namespace, repository)
+    return join(self._gun_prefix, namespace, repository)
   
   def _parse_signed(self, json_response):
     """ Attempts to parse the targets from a metadata response """
diff --git a/util/tufmetadata/test/test_tufmetadata.py b/util/tufmetadata/test/test_tufmetadata.py
index f0cec63b1..78046df86 100644
--- a/util/tufmetadata/test/test_tufmetadata.py
+++ b/util/tufmetadata/test/test_tufmetadata.py
@@ -33,6 +33,21 @@ valid_response = {
   ]
 }
 
+@pytest.mark.parametrize('tuf_prefix,server_hostname,namespace,repo,gun', [
+  ("quay.dev", "quay.io", "ns", "repo", "quay.dev/ns/repo"),
+  (None, "quay.io", "ns", "repo", "quay.io/ns/repo"),
+  ("quay.dev/", "quay.io", "ns", "repo", "quay.dev/ns/repo"),
+  (None, "quay.io/", "ns", "repo", "quay.io/ns/repo"),
+  (None, "localhost:5000/", "ns", "repo", "localhost:5000/ns/repo"),
+  (None, "localhost:5000", "ns", "repo", "localhost:5000/ns/repo"),
+])
+def test_gun(tuf_prefix, server_hostname, namespace, repo, gun):
+  app = Flask(__name__)
+  app.config.from_object(testconfig.TestConfig())
+  app.config['TUF_GUN_PREFIX'] = tuf_prefix
+  app.config['SERVER_HOSTNAME'] = server_hostname
+  tuf_api = api.TUFMetadataAPI(app, app.config)
+  assert gun == tuf_api._gun(namespace, repo)
 
 @pytest.mark.parametrize('response_code,response_body,expected', [
   (200, valid_response, (valid_response['signed']['targets'], '2020-03-30T18:55:26.594764859-04:00')),