diff --git a/pagure/lib/git.py b/pagure/lib/git.py
index d9b9d12..b2322e1 100644
--- a/pagure/lib/git.py
+++ b/pagure/lib/git.py
@@ -1399,7 +1399,12 @@ def get_diff_info(repo_obj, orig_repo, branch_from, branch_to, prid=None):
     :kwarg prid: the identifier of the pull-request to
 
     '''
-    frombranch = repo_obj.lookup_branch(branch_from)
+    try:
+        frombranch = repo_obj.lookup_branch(branch_from)
+    except ValueError:
+        raise pagure.exceptions.BranchNotFoundException(
+            'Branch %s does not exist' % branch_from
+        )
     if not frombranch and not repo_obj.is_empty and prid is None:
         raise pagure.exceptions.BranchNotFoundException(
             'Branch %s does not exist' % branch_from
@@ -1407,7 +1412,12 @@ def get_diff_info(repo_obj, orig_repo, branch_from, branch_to, prid=None):
 
     branch = None
     if branch_to:
-        branch = orig_repo.lookup_branch(branch_to)
+        try:
+            branch = orig_repo.lookup_branch(branch_to)
+        except ValueError:
+            raise pagure.exceptions.BranchNotFoundException(
+                'Branch %s does not exist' % branch_to
+            )
         local_branches = orig_repo.listall_branches(pygit2.GIT_BRANCH_LOCAL)
         if not branch and local_branches:
             raise pagure.exceptions.BranchNotFoundException(
diff --git a/tests/test_pagure_flask_ui_fork.py b/tests/test_pagure_flask_ui_fork.py
index 842470e..98d1eea 100644
--- a/tests/test_pagure_flask_ui_fork.py
+++ b/tests/test_pagure_flask_ui_fork.py
@@ -1692,6 +1692,30 @@ index 0000000..2a552bb
             self.assertEqual(output.status_code, 200)
 
     @patch('pagure.lib.notify.send_email')
+    def test_new_request_pull_branch_space(self, send_email):
+        """ Test the new_request_pull endpoint. """
+        send_email.return_value = True
+
+        self.test_fork_project()
+
+        tests.create_projects_git(
+            os.path.join(self.path, 'requests'), bare=True)
+
+        repo = pagure.lib.get_authorized_project(self.session, 'test')
+        fork = pagure.lib.get_authorized_project(self.session, 'test', user='foo')
+
+        self.set_up_git_repo(
+            new_project=fork, branch_from='feature', mtype='FF')
+
+        user = tests.FakeUser(username = 'pingou')
+        with tests.user_set(self.app.application, user):
+            output = self.app.get('/test/diff/master..foo bar')
+            self.assertEqual(output.status_code, 400)
+            output_text = output.get_data(as_text=True)
+            self.assertIn(
+                '<p>Branch foo bar does not exist</p>', output_text)
+
+    @patch('pagure.lib.notify.send_email')
     def test_new_request_pull(self, send_email):
         """ Test the new_request_pull endpoint. """
         send_email.return_value = True