diff --git a/doc/src/sgml/mvcc.sgml b/doc/src/sgml/mvcc.sgml
index 24613e3c75..a93b31ae6d 100644
--- a/doc/src/sgml/mvcc.sgml
+++ b/doc/src/sgml/mvcc.sgml
@@ -971,6 +971,7 @@ ERROR:  could not serialize access due to read/write dependencies among transact
 
         <para>
          Acquired by <command>CREATE COLLATION</command>,
+         <command>ALTER ROLE</command>,
          <command>CREATE TRIGGER</command>, and many forms of
          <command>ALTER TABLE</command> (see <xref linkend="sql-altertable"/>).
         </para>
diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
index f2941352d7..d2e300d949 100644
--- a/src/backend/commands/user.c
+++ b/src/backend/commands/user.c
@@ -671,9 +671,11 @@ AlterRole(AlterRoleStmt *stmt)
 		bypassrls = intVal(dbypassRLS->arg);
 
 	/*
-	 * Scan the pg_authid relation to be certain the user exists.
+	 * Scan the pg_authid relation to be certain the user exists. Take
+	 * ShareRowExclusiveLock to prevent other sessions to update this
+	 * tuple in parallel with another ALTER ROLE command.
 	 */
-	pg_authid_rel = heap_open(AuthIdRelationId, RowExclusiveLock);
+	pg_authid_rel = heap_open(AuthIdRelationId, ShareRowExclusiveLock);
 	pg_authid_dsc = RelationGetDescr(pg_authid_rel);
 
 	tuple = get_rolespec_tuple(stmt->role);