diff --git a/services/notebooks/notebooks_service.py b/services/notebooks/notebooks_service.py
index bef88aa410..2267b83bdc 100644
--- a/services/notebooks/notebooks_service.py
+++ b/services/notebooks/notebooks_service.py
@@ -49,7 +49,7 @@
 def _server_name(namespace, project, commit_sha):
     """Form a DNS-safe server name."""
     escape = lambda x: escapism.escape(
-        x, safe=set(string.ascii_lowercase + string.digits)
+        x, safe=set(string.ascii_lowercase + string.digits, escape_char='-')
     )
     return '{namespace}-{project}-{commit_sha}'.format(
         namespace=escape(namespace)[:10],