diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index d07e51fb65..da491e14ef 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.288.2.5 2010/07/29 19:23:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.288.2.6 2010/08/03 15:47:16 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -4524,6 +4524,15 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	/* Advance command counter in case same table is visited multiple times */
 	CommandCounterIncrement();
 
+	/*
+	 * If the constraint got merged with an existing constraint, we're done.
+	 * We mustn't recurse to child tables in this case, because they've already
+	 * got the constraint, and visiting them again would lead to an incorrect
+	 * value for coninhcount.
+	 */
+	if (newcons == NIL)
+		return;
+
 	/*
 	 * Propagate to children as appropriate.  Unlike most other ALTER
 	 * routines, we have to do this one level of recursion at a time; we can't