diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 1762782efa1..5f3e8e463ca 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.116.2.2 2006/01/10 22:00:07 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.116.2.3 2008/04/05 01:58:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -935,6 +935,16 @@ addRangeTableEntryForJoin(ParseState *pstate,
 	Alias	   *eref;
 	int			numaliases;
 
+	/*
+	 * Fail if join has too many columns --- we must be able to reference
+	 * any of the columns with an AttrNumber.
+	 */
+	if (list_length(aliasvars) > MaxAttrNumber)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("joins can have at most %d columns",
+						MaxAttrNumber)));
+
 	rte->rtekind = RTE_JOIN;
 	rte->relid = InvalidOid;
 	rte->subquery = NULL;
diff --git a/src/include/access/attnum.h b/src/include/access/attnum.h
index 7a4822e63f7..d129af0a876 100644
--- a/src/include/access/attnum.h
+++ b/src/include/access/attnum.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/attnum.h,v 1.21 2005/05/25 21:40:42 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/attnum.h,v 1.21.2.1 2008/04/05 01:58:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 typedef int16 AttrNumber;
 
 #define InvalidAttrNumber		0
+#define MaxAttrNumber			32767
 
 /* ----------------
  *		support macros