diff --git a/doc/ref/data-rep.texi b/doc/ref/data-rep.texi
index ba2011a52..daa22b303 100644
--- a/doc/ref/data-rep.texi
+++ b/doc/ref/data-rep.texi
@@ -46,7 +46,7 @@
 @c essay @sp 10
 @c essay @comment The title is printed in a large font.
 @c essay @title Data Representation in Guile
-@c essay @subtitle $Id: data-rep.texi,v 1.13 2003-06-21 23:02:58 kryde Exp $
+@c essay @subtitle $Id: data-rep.texi,v 1.14 2003-08-29 23:32:21 kryde Exp $
 @c essay @subtitle For use with Guile @value{VERSION}
 @c essay @author Jim Blandy
 @c essay @author Free Software Foundation
@@ -1918,6 +1918,11 @@ while code is still using it.
 Create a reference to the given object or objects, so they're certain
 to be present on the stack or in a register and hence will not be
 freed by the garbage collector before this point.
+
+Note that these functions can only be applied to ordinary C local
+variables (ie.@: ``automatics'').  Objects held in global or static
+variables or some malloced block or the like cannot be protected with
+this mechanism.
 @end deftypefn
 
 For example, consider a procedure to convert image data to a list of