diff --git a/pagure/ui/repo.py b/pagure/ui/repo.py
index 73ddfae..1ea7dd2 100644
--- a/pagure/ui/repo.py
+++ b/pagure/ui/repo.py
@@ -960,8 +960,13 @@ def view_tree(repo, identifier=None, username=None, namespace=None):
             except (ValueError, TypeError):
                 # If it's not a commit id then it's part of the filename
                 if not repo_obj.head_is_unborn:
-                    commit = repo_obj[repo_obj.head.target]
                     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 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):