diff --git a/ice-9/boot-9.scm b/ice-9/boot-9.scm
index 16254d32d..1aee82d60 100644
--- a/ice-9/boot-9.scm
+++ b/ice-9/boot-9.scm
@@ -1702,6 +1702,9 @@
   (lambda (symbol)
     (symbol-append prefix symbol)))
 
+;; This function is called from "modules.c".  If you change it, be
+;; sure to update "modules.c" as well.
+
 (define (process-define-module args)
   (let* ((module-id (car args))
          (module (resolve-module module-id #f))
@@ -1796,6 +1799,9 @@
 
 (define autoloads-in-progress '())
 
+;; This function is called from "modules.c".  If you change it, be
+;; sure to update "modules.c" as well.
+
 (define (try-module-autoload module-name)
   (let* ((reverse-name (reverse module-name))
 	 (name (symbol->string (car reverse-name)))
@@ -2553,6 +2559,9 @@
 ;; The guts of the use-modules macro.  Add the interfaces of the named
 ;; modules to the use-list of the current module, in order.
 
+;; This function is called by "modules.c".  If you change it, be sure
+;; to change scm_c_use_module as well.
+
 (define (process-use-modules module-interface-args)
   (for-each (lambda (mif-args)
 	      (let ((mod-iface (apply resolve-interface mif-args)))
@@ -2619,7 +2628,10 @@
 	 (defmacro ,@args))))))
 
 ;; Export a local variable
-;;
+
+;; This function is called from "modules.c".  If you change it, be
+;; sure to update "modules.c" as well.
+
 (define (module-export! m names)
   (let ((public-i (module-public-interface m)))
     (for-each (lambda (name)