diff --git a/lib/auth.py b/lib/auth.py
index bddb9f6..09af99a 100644
--- a/lib/auth.py
+++ b/lib/auth.py
@@ -27,14 +27,18 @@
   """Error accessing the token."""
 
 
-def GetAuthUtil(instance_id='latest'):
+# crbug:871831 default to last sha1 version.
+def GetAuthUtil(
+    instance_id='git_revision:fd059ace316e4dbcaa5afdcec9ed4a855c4f3c65'):
   """Returns a path to the authutil binary.
 
   This will download and install the authutil package if it is not already
   deployed.
 
   Args:
-    instance_id: The instance-id of the package to install. Defaults to 'latest'
+    instance_id: The instance-id of the package to install. Defaults to
+    'git_revision:fd059ace316e4dbcaa5afdcec9ed4a855c4f3c65' which is the last
+    SHA1 version.
 
   Returns:
     the path to the authutil binary.