diff --git a/sql/ha_innodb.cc b/sql/ha_innodb.cc
index b1f1911858d..5c73d36d9bc 100644
--- a/sql/ha_innodb.cc
+++ b/sql/ha_innodb.cc
@@ -4143,9 +4143,12 @@ static void free_share(INNOBASE_SHARE *share)
 
 /*********************************************************************
 Converts a MySQL table lock stored in the 'lock' field of the handle to
-a proper type before storing the lock. MySQL also calls this when it
-releases a lock. */
-
+a proper type before storing pointer to the lock into an array of pointers.
+MySQL also calls this if it wants to reset some table locks to a not-locked
+state during the processing of an SQL query. An example is that during a
+SELECT the read lock is released early on the 'const' tables where we only
+fetch one row. MySQL does not call this when it releases all locks at the
+end of an SQL statement. */
 
 THR_LOCK_DATA**
 ha_innobase::store_lock(