diff --git a/src/include/c.h b/src/include/c.h
index 0a8a129c02..9053628d62 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: c.h,v 1.119 2002/04/25 02:56:56 tgl Exp $
+ * $Id: c.h,v 1.120 2002/04/30 19:53:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -420,7 +420,9 @@ typedef Oid oidvector[INDEX_MAX_KEYS];
 /*
  * We want NameData to have length NAMEDATALEN and int alignment,
  * because that's how the data type 'name' is defined in pg_type.
- * Use a union to make sure the compiler agrees.
+ * Use a union to make sure the compiler agrees.  Note that NAMEDATALEN
+ * must be a multiple of sizeof(int), else sizeof(NameData) will probably
+ * not come out equal to NAMEDATALEN.
  */
 typedef union nameData
 {
diff --git a/src/include/postgres_ext.h b/src/include/postgres_ext.h
index 0699cebdf8..3249ce4350 100644
--- a/src/include/postgres_ext.h
+++ b/src/include/postgres_ext.h
@@ -15,7 +15,7 @@
  *	use header files that are otherwise internal to Postgres to interface
  *	with the backend.
  *
- * $Id: postgres_ext.h,v 1.9 2001/10/28 06:25:59 momjian Exp $
+ * $Id: postgres_ext.h,v 1.10 2002/04/30 19:53:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -36,7 +36,8 @@ typedef unsigned int Oid;
 
 /*
  * NAMEDATALEN is the max length for system identifiers (e.g. table names,
- * attribute names, function names, etc.)
+ * attribute names, function names, etc).  It must be a multiple of
+ * sizeof(int) (typically 4).
  *
  * NOTE that databases with different NAMEDATALEN's cannot interoperate!
  */