diff --git a/docs/source/reference/services.md b/docs/source/reference/services.md
index 7686d4a4..ec446c8e 100644
--- a/docs/source/reference/services.md
+++ b/docs/source/reference/services.md
@@ -360,7 +360,7 @@ and taking note of the following process:
 
 An example of using an Externally-Managed Service and authentication is
 in [nbviewer README][nbviewer example] section on securing the notebook viewer,
-and an example of its configuration is found [here](https://github.com/jupyter/nbviewer/blob/master/nbviewer/providers/base.py#L94).
+and an example of its configuration is found [here](https://github.com/jupyter/nbviewer/blob/ed942b10a52b6259099e2dd687930871dc8aac22/nbviewer/providers/base.py#L95).
 nbviewer can also be run as a Hub-Managed Service as described [nbviewer README][nbviewer example]
 section on securing the notebook viewer.