diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 970abd4..0bcdd76 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -2807,7 +2807,8 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
  * Function is called before and after parsing, so it must give same
  * answer each time it is called. Some subcommands are transformed
  * into other subcommand types, so the transform must never be made to a
- * lower lock level than previously assigned. All transforms are noted below.
+ * lock level different than previously assigned. All transforms are noted
+ * below.
  *
  * Since this is called before we lock the table we cannot use table metadata
  * to influence the type of lock we acquire.
@@ -2837,6 +2838,7 @@ AlterTableGetLockLevel(List *cmds)
 	 */
 	ListCell   *lcmd;
 	LOCKMODE	lockmode = ShareUpdateExclusiveLock;
+	bool		is_init = false;
 
 	foreach(lcmd, cmds)
 	{
@@ -3057,10 +3059,22 @@ AlterTableGetLockLevel(List *cmds)
 		}
 
 		/*
-		 * Take the greatest lockmode from any subcommand
+		 * At the first command evaluated, take the lock corresponding to
+		 * it. When looking at the next commands, check if the lock taken
+		 * is different than the first one taken and enforce it to
+		 * AccessExclusiveLock, which is the only lock super-seeding all
+		 * the others.
 		 */
-		if (cmd_lockmode > lockmode)
+		if (!is_init)
+		{
 			lockmode = cmd_lockmode;
+			is_init = true;
+		}
+		else
+		{
+			if (cmd_lockmode != lockmode)
+				lockmode = AccessExclusiveLock;
+		}
 	}
 
 	return lockmode;