diff --git a/server-ca/redis_lock.py b/server-ca/redis_lock.py
index ac990e511..530cd0a4e 100644
--- a/server-ca/redis_lock.py
+++ b/server-ca/redis_lock.py
@@ -20,7 +20,8 @@
 #
 # The optional one_shot parameter causes the attempt to acquire the
 # lock to instead raise a KeyError exception if someone else is already
-# holding a valid lock.
+# holding a valid lock.  This is used in situations where a process
+# doesn't insist on doing the actions guarded by the lock.
 
 import time, random