diff --git a/trac/versioncontrol/web_ui/changeset.py b/trac/versioncontrol/web_ui/changeset.py
index 874b4a93a0..30fdc860e7 100644
--- a/trac/versioncontrol/web_ui/changeset.py
+++ b/trac/versioncontrol/web_ui/changeset.py
@@ -1173,7 +1173,7 @@ def process_request(self, req):
         rm = RepositoryManager(self.env)
 
         if req.is_xhr:
-            dirname, prefix = posixpath.split(req.args.get('term'))
+            dirname, prefix = posixpath.split(req.args.get('term') or '')
             prefix = prefix.lower()
             reponame, repos, path = rm.get_repository_by_path(dirname)
             # an entry is a (isdir, name, path) tuple
@@ -1196,7 +1196,7 @@ def kind_order(entry):
                      for isdir, name, path in sorted(entries, key=kind_order)
                                            if name.lower().startswith(prefix)]
 
-            content = to_json(paths)
+            content = to_json(paths).encode('utf-8')
             req.send(content, 'application/json', 200)
 
         # -- retrieve arguments
diff --git a/trac/versioncontrol/web_ui/tests/changeset.py b/trac/versioncontrol/web_ui/tests/changeset.py
index b48179d339..f3d512dabc 100644
--- a/trac/versioncontrol/web_ui/tests/changeset.py
+++ b/trac/versioncontrol/web_ui/tests/changeset.py
@@ -15,7 +15,8 @@
 
 from trac.core import TracError
 from trac.test import EnvironmentStub, MockRequest, makeSuite
-from trac.versioncontrol.web_ui.changeset import ChangesetModule
+from trac.versioncontrol.web_ui.changeset import AnyDiffModule, ChangesetModule
+from trac.web.api import RequestDone
 
 
 class ChangesetModuleTestCase(unittest.TestCase):
@@ -30,9 +31,35 @@ def test_default_repository_not_configured(self):
         self.assertRaises(TracError, self.cm.process_request, req)
 
 
+class AnyDiffModuleTestCase(unittest.TestCase):
+
+    def setUp(self):
+        self.env = EnvironmentStub()
+        self.mod = AnyDiffModule(self.env)
+
+    def test_normal(self):
+        req = MockRequest(self.env, path_info='/diff', args={'term': '/'})
+        req.environ['HTTP_X_REQUESTED_WITH'] = 'XMLHttpRequest'
+        self.assertTrue(self.mod.match_request(req))
+        self.assertRaises(RequestDone, self.mod.process_request, req)
+        self.assertEqual(b'[]', req.response_sent.getvalue())
+        self.assertEqual('application/json;charset=utf-8',
+                         req.headers_sent.get('Content-Type'))
+
+    def test_without_term(self):
+        req = MockRequest(self.env, path_info='/diff')
+        req.environ['HTTP_X_REQUESTED_WITH'] = 'XMLHttpRequest'
+        self.assertTrue(self.mod.match_request(req))
+        self.assertRaises(RequestDone, self.mod.process_request, req)
+        self.assertEqual(b'[]', req.response_sent.getvalue())
+        self.assertEqual('application/json;charset=utf-8',
+                         req.headers_sent.get('Content-Type'))
+
+
 def test_suite():
     suite = unittest.TestSuite()
     suite.addTest(makeSuite(ChangesetModuleTestCase))
+    suite.addTest(makeSuite(AnyDiffModuleTestCase))
     return suite