diff --git a/core/net/mac/mac.h b/core/net/mac/mac.h
index d5ebcf6d6..acaf43110 100644
--- a/core/net/mac/mac.h
+++ b/core/net/mac/mac.h
@@ -28,7 +28,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: mac.h,v 1.1 2007/05/25 06:40:19 adamdunkels Exp $
+ * $Id: mac.h,v 1.2 2008/02/24 21:05:28 adamdunkels Exp $
  */
 
 /**
@@ -58,7 +58,7 @@ struct mac_driver {
   int (* on)(void);
 
   /** Turn the MAC layer off. */
-  int (* off)(void);
+  int (* off)(int keep_radio_on);
 };
 
 
diff --git a/core/net/mac/nullmac.c b/core/net/mac/nullmac.c
index f2ea792e3..5a8dcc8de 100644
--- a/core/net/mac/nullmac.c
+++ b/core/net/mac/nullmac.c
@@ -28,7 +28,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: nullmac.c,v 1.6 2007/12/23 14:56:54 oliverschmidt Exp $
+ * $Id: nullmac.c,v 1.7 2008/02/24 21:05:28 adamdunkels Exp $
  */
 
 /**
@@ -81,9 +81,13 @@ on(void)
 }
 /*---------------------------------------------------------------------------*/
 static int
-off(void)
+off(int keep_radio_on)
 {
-  return radio->off();
+  if(keep_radio_on) {
+    return radio->on();
+  } else {
+    return radio->off();
+  }
 }
 /*---------------------------------------------------------------------------*/
 const struct mac_driver nullmac_driver = {