diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 563bcda..b7c87b9 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -13175,7 +13175,28 @@ RangeVarCallbackForAlterRelation(const RangeVar *rv, Oid relid, Oid oldrelid,
 		reltype = ((AlterObjectSchemaStmt *) stmt)->objectType;
 
 	else if (IsA(stmt, AlterTableStmt))
-		reltype = ((AlterTableStmt *) stmt)->relkind;
+	{
+		AlterTableStmt *alterstmt = (AlterTableStmt *)stmt;
+		ListCell *lc;
+
+		reltype = alterstmt->relkind;
+
+		foreach (lc, alterstmt->cmds)
+		{
+			AlterTableCmd *cmd = lfirst_node(AlterTableCmd, lc);
+			Assert(IsA(cmd, AlterTableCmd));
+
+			/*
+			 * Though NO INHERIT doesn't modify the parent, concurrent
+			 * expansion of inheritances will see a false child. We must
+			 * acquire lock on the parent when dropping inheritance, but no
+			 * need to ascend further.
+			 */
+			if (cmd->subtype == AT_DropInherit)
+				RangeVarGetRelid((RangeVar *)cmd->def,
+								 AccessExclusiveLock, false);
+		}
+	}
 	else
 	{
 		reltype = OBJECT_TABLE; /* placate compiler */