--- src/sys/bus/cam/scsi/scsi_ch.c	2007/11/18 17:53:01	1.22
+++ src/sys/bus/cam/scsi/scsi_ch.c	2007/11/21 21:28:41	1.23
@@ -319,6 +319,8 @@ chasync(void *callback_arg, u_int32_t co
 		cam_status status;
 
 		cgd = (struct ccb_getdev *)arg;
+		if (cgd == NULL)
+			break;
 
 		if (SID_TYPE(&cgd->inq_data)!= T_CHANGER)
 			break;