diff --git a/drivers/libshut.c b/drivers/libshut.c
index c0b8ffea6f..f375db295d 100644
--- a/drivers/libshut.c
+++ b/drivers/libshut.c
@@ -626,7 +626,7 @@ void setline(int upsfd, int set)
 int shut_synchronise(int upsfd)
 {
 	int retCode = 0;
-	u_char c = SHUT_SYNC_OFF, reply;
+	unsigned char c = SHUT_SYNC_OFF, reply;
 	int try;
 
 	upsdebugx (2, "entering shut_synchronise()");
@@ -672,10 +672,10 @@ int shut_synchronise(int upsfd)
 /*!
  * Compute a SHUT checksum for the packet "buf"
  */
-u_char shut_checksum(const u_char *buf, int bufsize)
+unsigned char shut_checksum(const unsigned char *buf, int bufsize)
 {
 	int i;
-	u_char chk=0;
+	unsigned char chk=0;
 
 	for(i=0; i<bufsize; i++)
 		chk^=buf[i];
@@ -685,14 +685,14 @@ u_char shut_checksum(const u_char *buf, int bufsize)
 }
 
 
-int shut_packet_recv(int upsfd, u_char *Buf, int datalen)
+int shut_packet_recv(int upsfd, unsigned char *Buf, int datalen)
 {
-	u_char   Start[2];
-	u_char   Frame[8];
-	u_char   Chk[1];
-	u_short  Size=8;
-	u_short  Pos=0;
-	u_char   Retry=0;
+	unsigned char   Start[2];
+	unsigned char   Frame[8];
+	unsigned char   Chk[1];
+	unsigned short  Size=8;
+	unsigned short  Pos=0;
+	unsigned char   Retry=0;
 	int recv;
 	/* FIXME: use this
 	 * shut_data_t   sdata; */
@@ -845,7 +845,7 @@ int shut_get_string_simple(int upsfd, int index,
  *********************************************************************/
 
 /**********************************************************************
- * shut_get_descriptor(int desctype, u_char *pkt)
+ * shut_get_descriptor(int desctype, unsigned char *pkt)
  *
  * get descriptor specified by DescType and return it in Buf
  *
@@ -994,7 +994,7 @@ int shut_control_msg(int upsfd, int requesttype, int request,
 int shut_wait_ack(int upsfd)
 {
 	int retCode = -1;
-	u_char c = '\0';
+	unsigned char c = '\0';
 
 	ser_get_char(upsfd, &c, SHUT_TIMEOUT/1000, 0);
 	if (c == SHUT_OK)
diff --git a/drivers/riello_ser.c b/drivers/riello_ser.c
index f1075462bd..028df5cb2d 100644
--- a/drivers/riello_ser.c
+++ b/drivers/riello_ser.c
@@ -121,11 +121,11 @@ static int char_read (char *bytes, int size, int read_timeout)
  * returns 0 on success, -1 on error, -2 on timeout
  *
  **********************************************************************/
-int serial_read (int read_timeout, u_char *readbuf)
+int serial_read (int read_timeout, unsigned char *readbuf)
 {
-	static u_char cache[512];
-	static u_char *cachep = cache;
-	static u_char *cachee = cache;
+	static unsigned char cache[512];
+	static unsigned char *cachep = cache;
+	static unsigned char *cachee = cache;
 	int recv;
 	*readbuf = '\0';
 
diff --git a/drivers/snmp-ups.c b/drivers/snmp-ups.c
index 74b58c99ab..9e1c90b759 100644
--- a/drivers/snmp-ups.c
+++ b/drivers/snmp-ups.c
@@ -577,7 +577,7 @@ void nut_snmp_init(const char *type, const char *hostname)
 		if(g_snmp_sess.securityLevel != SNMP_SEC_LEVEL_NOAUTH) {
 			if (generate_Ku(g_snmp_sess.securityAuthProto,
 				g_snmp_sess.securityAuthProtoLen,
-				(u_char *) authPassword, strlen(authPassword),
+				(unsigned char *) authPassword, strlen(authPassword),
 				g_snmp_sess.securityAuthKey,
 				&g_snmp_sess.securityAuthKeyLen) !=
 				SNMPERR_SUCCESS) {
@@ -604,7 +604,7 @@ void nut_snmp_init(const char *type, const char *hostname)
 			g_snmp_sess.securityPrivKeyLen = USM_PRIV_KU_LEN;
 			if (generate_Ku(g_snmp_sess.securityAuthProto,
 				g_snmp_sess.securityAuthProtoLen,
-				(u_char *) privPassword, strlen(privPassword),
+				(unsigned char *) privPassword, strlen(privPassword),
 				g_snmp_sess.securityPrivKey,
 				&g_snmp_sess.securityPrivKeyLen) !=
 				SNMPERR_SUCCESS) {
@@ -790,7 +790,7 @@ static bool_t decode_str(struct snmp_pdu *pdu, char *buf, size_t buf_len, info_l
 			buf_len - 1 : pdu->variables->val_len;
 		/* Test for hexadecimal values */
 		int hex = 0, x;
-		u_char *cp;
+		unsigned char *cp;
 		for(cp = pdu->variables->val.string, x = 0; x < (int)pdu->variables->val_len; x++, cp++) {
 			if (!(isprint(*cp) || isspace(*cp))) {
 				hex = 1;
diff --git a/tools/nut-scanner/scan_eaton_serial.c b/tools/nut-scanner/scan_eaton_serial.c
index 1a4e5c71e3..6a0a7ae209 100644
--- a/tools/nut-scanner/scan_eaton_serial.c
+++ b/tools/nut-scanner/scan_eaton_serial.c
@@ -121,7 +121,7 @@ unsigned char calc_checksum(const unsigned char *buf)
 int shut_synchronise(int upsfd)
 {
 	int try;
-	u_char reply = '\0';
+	unsigned char reply = '\0';
 
 	/* Sync with the UPS according to notification */
 	for (try = 0; try < MAX_TRY; try++) {
diff --git a/tools/nut-scanner/scan_snmp.c b/tools/nut-scanner/scan_snmp.c
index 6471f64435..d2eeec29c6 100644
--- a/tools/nut-scanner/scan_snmp.c
+++ b/tools/nut-scanner/scan_snmp.c
@@ -96,7 +96,7 @@ static int (*nut_snmp_oid_compare) (const oid *in_name1, size_t len1,
 			const oid *in_name2, size_t len2);
 static void (*nut_snmp_free_pdu) (netsnmp_pdu *pdu);
 static int (*nut_generate_Ku)(const oid * hashtype, u_int hashtype_len,
-			u_char * P, size_t pplen, u_char * Ku, size_t * kulen);
+			unsigned char * P, size_t pplen, unsigned char * Ku, size_t * kulen);
 static char* (*nut_snmp_out_toggle_options)(char *options);
 static const char * (*nut_snmp_api_errstring) (int snmp_errnumber);
 static int (*nut_snmp_errno);
@@ -511,7 +511,7 @@ static int init_session(struct snmp_session * snmp_sess, nutscan_snmp_t * sec)
 		 * our passphrase (must be at least 8 characters long) */
 		if ((*nut_generate_Ku)(snmp_sess->securityAuthProto,
 					snmp_sess->securityAuthProtoLen,
-					(u_char *) sec->authPassword,
+					(unsigned char *) sec->authPassword,
 					strlen(sec->authPassword),
 					snmp_sess->securityAuthKey,
 					&snmp_sess->securityAuthKeyLen)
@@ -553,7 +553,7 @@ static int init_session(struct snmp_session * snmp_sess, nutscan_snmp_t * sec)
 		snmp_sess->securityPrivKeyLen = USM_PRIV_KU_LEN;
 		if ((*nut_generate_Ku)(snmp_sess->securityAuthProto,
 					snmp_sess->securityAuthProtoLen,
-					(u_char *) sec->privPassword,
+					(unsigned char *) sec->privPassword,
 					strlen(sec->privPassword),
 					snmp_sess->securityPrivKey,
 					&snmp_sess->securityPrivKeyLen)