diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 2a32960f9e375d9210296c2fac29db09542f3123..92d1130606833aa5ce5a888827fbc187bd2a91f8 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/transam.c,v 1.58 2004/08/22 02:41:57 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/transam.c,v 1.59 2004/08/28 21:58:59 tgl Exp $
  *
  * NOTES
  *	  This file contains the high level access-method interface to the
@@ -258,6 +258,7 @@ TransactionIdDidAbort(TransactionId transactionId)
 		if (TransactionIdPrecedes(transactionId, RecentXmin))
 			return true;
 		parentXid = SubTransGetParent(transactionId);
+		Assert(TransactionIdIsValid(parentXid));
 		return TransactionIdDidAbort(parentXid);
 	}