diff --git a/docs/administration-guide.rst b/docs/administration-guide.rst
index bcc8e00b..69b2fa48 100644
--- a/docs/administration-guide.rst
+++ b/docs/administration-guide.rst
@@ -211,6 +211,10 @@ Environment Variables
   When set, this value is used to access the secret encryption key (if
   protected by password).
 
+``PBS_FINGERPRINT`` When set, this value is used to verify the server
+  certificate (only used if the system CA certificates cannot
+  validate the certificate).
+
 
 Creating Backups
 ~~~~~~~~~~~~~~~~