diff --git a/pagure/ui/repo.py b/pagure/ui/repo.py
index bc95201..3f659dc 100644
--- a/pagure/ui/repo.py
+++ b/pagure/ui/repo.py
@@ -962,11 +962,12 @@ def view_tree(repo, identifier=None, username=None, namespace=None):
                 if not repo_obj.head_is_unborn:
                     branchname = repo_obj.head.shorthand
                     commit = repo_obj[repo_obj.head.target]
-                    flask.flash(
-                        "'%s' not found in the git repository, going back to: "
-                        "%s" % (identifier, branchname),
-                        "error",
-                    )
+                    if identifier:
+                        flask.flash(
+                            "'%s' not found in the git repository, going back "
+                            "to: %s" % (identifier, branchname),
+                            "error",
+                        )
         # If we're arriving here from the release page, we may have a Tag
         # where we expected a commit, in this case, get the actual commit
         if isinstance(commit, pygit2.Tag):
diff --git a/tests/test_pagure_flask_ui_repo.py b/tests/test_pagure_flask_ui_repo.py
index 1e89014..ab86f71 100644
--- a/tests/test_pagure_flask_ui_repo.py
+++ b/tests/test_pagure_flask_ui_repo.py
@@ -3175,6 +3175,30 @@ index 0000000..fb7093d
         self.assertFalse(
             'No content found in this repository' in output_text)
 
+        # View tree, no identifier:
+        output = self.app.get('/test/tree/')
+        self.assertEqual(output.status_code, 200)
+        output_text = output.get_data(as_text=True)
+        self.assertIn('<title>Tree - test - Pagure</title>', output_text)
+        self.assertIn('README.rst', output_text)
+        self.assertNotIn(
+            'No content found in this repository', output_text)
+        self.assertNotIn(
+            "&#39;None&#39; not found in the git repository, going back to: "
+            "master", output_text)
+
+        # View tree, invalid identifier:
+        output = self.app.get('/test/tree/invalid')
+        self.assertEqual(output.status_code, 200)
+        output_text = output.get_data(as_text=True)
+        self.assertIn('<title>Tree - test - Pagure</title>', output_text)
+        self.assertIn('README.rst', output_text)
+        self.assertNotIn(
+            'No content found in this repository', output_text)
+        self.assertIn(
+            "&#39;invalid&#39; not found in the git repository, going back "
+            "to: master", output_text)
+
         # View tree by branch
         output = self.app.get('/test/tree/master')
         self.assertEqual(output.status_code, 200)