diff --git a/doc/src/sgml/ref/alter_sequence.sgml b/doc/src/sgml/ref/alter_sequence.sgml
index 5c912ab892..a261ca8dc0 100644
--- a/doc/src/sgml/ref/alter_sequence.sgml
+++ b/doc/src/sgml/ref/alter_sequence.sgml
@@ -300,6 +300,13 @@ ALTER SEQUENCE [ IF EXISTS ] <replaceable class="parameter">name</replaceable> S
   </para>
 
   <para>
+   <command>ALTER SEQUENCE</command> uses
+   <literal>ACCESS EXCLUSIVE LOCK</literal> for <literal>OWNED BY</>,
+   <literal>OWNER TO</>, <literal>RENAME TO</>, and <literal>SET SCHEMA</>,
+   and <literal>SHARE UPDATE EXCLUSIVE</literal> otherwise.
+  </para>
+
+  <para>
    <command>ALTER SEQUENCE</command> does not affect the <function>currval</>
    status for the sequence.  (Before <productname>PostgreSQL</productname>
    8.3, it sometimes did.)
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index ad28225b36..ab7903d8aa 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -423,7 +423,8 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 	HeapTuple	tuple;
 
 	/* Open and lock sequence. */
-	relid = RangeVarGetRelid(stmt->sequence, AccessShareLock, stmt->missing_ok);
+	relid = RangeVarGetRelid(stmt->sequence, ShareUpdateExclusiveLock,
+							 stmt->missing_ok);
 	if (relid == InvalidOid)
 	{
 		ereport(NOTICE,
diff --git a/src/include/storage/lockdefs.h b/src/include/storage/lockdefs.h
index bfeb8779f7..0183185d1b 100644
--- a/src/include/storage/lockdefs.h
+++ b/src/include/storage/lockdefs.h
@@ -37,7 +37,8 @@ typedef int LOCKMODE;
 #define RowShareLock			2		/* SELECT FOR UPDATE/FOR SHARE */
 #define RowExclusiveLock		3		/* INSERT, UPDATE, DELETE */
 #define ShareUpdateExclusiveLock 4		/* VACUUM (non-FULL),ANALYZE, CREATE
-										 * INDEX CONCURRENTLY */
+										 * INDEX CONCURRENTLY, ALTER SEQUENCE
+										 * (for non-reversible changes) */
 #define ShareLock				5		/* CREATE INDEX (WITHOUT CONCURRENTLY) */
 #define ShareRowExclusiveLock	6		/* like EXCLUSIVE MODE, but allows ROW
 										 * SHARE */