--- libaitpelco/src/aitpelco.c	2010/03/17 13:34:34	1.1.1.1.2.4
+++ libaitpelco/src/aitpelco.c	2010/03/23 01:25:43	1.1.1.1.2.5
@@ -3,7 +3,7 @@
 *  by Michael Pounov <misho@openbsd-bg.org>
 *
 * $Author: misho $
-* $Id: aitpelco.c,v 1.1.1.1.2.4 2010/03/17 13:34:34 misho Exp $
+* $Id: aitpelco.c,v 1.1.1.1.2.5 2010/03/23 01:25:43 misho Exp $
 *
 *************************************************************************/
 #include "global.h"
@@ -119,6 +119,11 @@ inline void *pelcoLoad(u_char *buffer)
 	pelco_p_t *pp;
 	void *p = NULL;
 
+	if (!buffer || !*buffer) {
+		pelcoSetErr(EINVAL, "invalid argument!\n");
+		return NULL;
+	}
+
 	switch (pelco_GetVersion(buffer)) {
 		case 'd':
 			if (pelco_GetCamNo(buffer) < FIRST_CAM_D) {
@@ -167,7 +172,7 @@ inline u_char pelcoAddCmdData(void * __restrict p, u_c
 	pelco_p_t *pp = (pelco_p_t *) p;
 	u_char *ptr = p;
 
-	if (!p) {
+	if (!p || !*ptr) {
 		pelcoSetErr(EINVAL, "invalid argument!\n");
 		return 0xFF;
 	}
@@ -229,7 +234,7 @@ inline u_char pelcoChkSum(void * __restrict p, u_char 
 	pelco_d_t *pd = (pelco_d_t *) p;
 	pelco_p_t *pp = (pelco_p_t *) p;
 
-	if (!p) {
+	if (!p || !*ptr) {
 		pelcoSetErr(EINVAL, "invalid argument!\n");
 		return 0xFF;
 	}