diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 180ba985129..bc5c54d2801 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.90.2.2 2005/05/29 17:10:52 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.90.2.3 2008/04/05 01:59:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1072,6 +1072,16 @@ 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 (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 16d16f5a9df..25f0d4ee368 100644
--- a/src/include/access/attnum.h
+++ b/src/include/access/attnum.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: attnum.h,v 1.17 2003/08/04 02:40:10 momjian Exp $
+ * $Id: attnum.h,v 1.17.4.1 2008/04/05 01:59:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,7 @@
 typedef int16 AttrNumber;
 
 #define InvalidAttrNumber		0
+#define MaxAttrNumber			32767
 
 /* ----------------
  *		support macros