--- sys/dev/ata/atapi-cd.c	Tue Apr 18 14:07:03 2006
+++ sys/dev/ata/atapi-cd.c.patched	Tue Apr 18 14:06:49 2006
@@ -192,9 +192,13 @@
 acd_geom_detach(void *arg, int flag)
 {   
     struct acd_softc *cdp = device_get_ivars(arg);
-
-    /* signal geom so we dont get any further requests */
-    g_wither_geom(cdp->gp, ENXIO);
+    
+    if (cdp != NULL) {
+        /* signal geom so we dont get any further requests */
+        g_wither_geom(cdp->gp, ENXIO);
+    } else {
+        device_printf(arg, "already detached\n");
+    }
 
     /* fail requests on the queue and any thats "in flight" for this device */
     ata_fail_requests(arg);