diff --git a/jupyterhub/services/service.py b/jupyterhub/services/service.py
index 546c8c78..894d45af 100644
--- a/jupyterhub/services/service.py
+++ b/jupyterhub/services/service.py
@@ -204,7 +204,7 @@ class Service(LoggingConfigurable):
 
     @property
     def prefix(self):
-        return url_path_join(self.base_url, 'services', self.name)
+        return url_path_join(self.base_url, 'services', self.name + '/')
 
     @property
     def proxy_path(self):
diff --git a/jupyterhub/singleuser.py b/jupyterhub/singleuser.py
index 6366f700..65c69164 100755
--- a/jupyterhub/singleuser.py
+++ b/jupyterhub/singleuser.py
@@ -180,6 +180,17 @@ class SingleUserNotebookApp(NotebookApp):
     def _base_url_default(self):
         return os.environ.get('JUPYTERHUB_SERVICE_PREFIX') or '/'
 
+    #Note: this may be removed if notebook module is >= 5.0.0b1
+    @validate('base_url')
+    def _validate_base_url(self, proposal):
+        """ensure base_url starts and ends with /"""
+        value = proposal.value
+        if not value.startswith('/'):
+            value = '/' + value
+        if not value.endswith('/'):
+            value = value + '/'
+        return value
+
     @default('cookie_name')
     def _cookie_name_default(self):
         if os.environ.get('JUPYTERHUB_SERVICE_NAME'):
diff --git a/requirements.txt b/requirements.txt
index 82528a48..7271e737 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 alembic
-traitlets>=4.3
+traitlets>=4.3.2
 tornado>=4.1
 jinja2
 pamela