diff --git a/adat/adat.c b/adat/adat.c
index 6a720eccf..5c40b4406 100644
--- a/adat/adat.c
+++ b/adat/adat.c
@@ -594,7 +594,7 @@ size_t trimwhitespace( char *out, size_t len, const char *str )
     }
 
     // Trim leading space
-    while(isspace(*str)) str++;
+    while(isspace((int)*str)) str++;
 
     if(*str == 0)  // All spaces?
     {
@@ -605,7 +605,7 @@ size_t trimwhitespace( char *out, size_t len, const char *str )
 
     // Trim trailing space
     end = (char *)(str + strlen(str) - 1);
-    while(end > str && isspace(*end))
+    while(end > str && isspace((int)*end))
     {
       *end = '\0';
       end--;
@@ -732,7 +732,7 @@ int adat_parse_freq( char                    *pcStr,
 
             // Get Freq Value from response string
 
-            while(( isalpha( *pcEnd ) == 0 ) ||
+            while(( isalpha( (int)*pcEnd ) == 0 ) ||
                   ( *pcEnd == '.' ))
             {
                 acValueBuf[ nI++ ] = *pcEnd;
@@ -748,7 +748,7 @@ int adat_parse_freq( char                    *pcStr,
             // Get Freq Unit from response string
 
             nI = 0;
-            while( isalpha( *pcEnd ) != 0 )
+            while( isalpha( (int)*pcEnd ) != 0 )
             {
                 acUnitBuf[ nI++ ] = *pcEnd;
                 pcEnd += sizeof( char );
diff --git a/kenwood/ic10.c b/kenwood/ic10.c
index 1adaa13b4..69e079170 100644
--- a/kenwood/ic10.c
+++ b/kenwood/ic10.c
@@ -53,7 +53,7 @@ int ic10_cmd_trim (char *data, int data_len) {
 				__func__, data_len);
 
        /* suck up additional spaces at end of the data buffer */
-        for (i=data_len; !isdigit(data[i-1]); i--) {
+        for (i=data_len; !isdigit((int)data[i-1]); i--) {
                data_len = data_len-1;
         	rig_debug(RIG_DEBUG_TRACE,"%s: data['%d'] is '%c'\n",
                                 __func__, i-1, data[i-1]);
diff --git a/kenwood/kenwood.c b/kenwood/kenwood.c
index a1ace6495..bcac1ddf0 100644
--- a/kenwood/kenwood.c
+++ b/kenwood/kenwood.c
@@ -1297,7 +1297,7 @@ int kenwood_get_level(RIG *rig, vfo_t vfo, setting_t level, value_t *val)
 
 		if (lvlbuf[2] == '0')
 			val->i = 0;
-		else if (isdigit(lvlbuf[2])) {
+		else if (isdigit((int)lvlbuf[2])) {
 			lvl = lvlbuf[2]-'0';
 			for (i=0; i<lvl && i<MAXDBLSTSIZ; i++) {
 				if (rig->state.preamp[i] == 0) {
diff --git a/rotorez/rotorez.c b/rotorez/rotorez.c
index 758d4d7e0..5f68b3139 100644
--- a/rotorez/rotorez.c
+++ b/rotorez/rotorez.c
@@ -420,7 +420,7 @@ static int rotorez_rot_get_position(ROT *rot, azimuth_t *azimuth, elevation_t *e
 		} else if (err == AZ_READ_LEN && az[0] == ';') {
 			/* Check if remaining chars are digits if az[0] == ';' */
 			for (p = az + 1;p < az + 4; p++)
-				if (isdigit(*p))
+				if (isdigit((int)*p))
 					continue;
 				else
 					err = -RIG_EINVAL;
@@ -493,14 +493,14 @@ static int erc_rot_get_position(ROT *rot, azimuth_t *azimuth, elevation_t *eleva
 		/* Check if remaining chars are digits if az[3] == ';' */
 		if (az[3] == ';') {
 			for (p = az; p < az + 3; p++)
-				if (isdigit(*p))
+				if (isdigit((int)*p))
 					continue;
 				else
 					err = -RIG_EINVAL;
 		} else if (az[0] == ';') {
 			/* Check if remaining chars are digits if az[0] == ';' */
 			for (p = az + 1;p < az + 4; p++)
-				if (isdigit(*p))
+				if (isdigit((int)*p))
 					continue;
 				else
 					err = -RIG_EINVAL;
diff --git a/src/parallel.c b/src/parallel.c
index bdb6fa219..1da21daf4 100644
--- a/src/parallel.c
+++ b/src/parallel.c
@@ -124,7 +124,9 @@
 int par_open(hamlib_port_t *port)
 {
 	int fd;
+#ifdef HAVE_LINUX_PPDEV_H
 	int mode;
+#endif
 
 	if (!port->pathname)
 		return -RIG_EINVAL;
diff --git a/tentec/orion.c b/tentec/orion.c
index 3225305bd..8ca1eaa4a 100644
--- a/tentec/orion.c
+++ b/tentec/orion.c
@@ -918,7 +918,7 @@ const char *tt565_get_info(RIG *rig)
 
 	/* filter out any non-graphic characters */
 	for (i=0; i < strlen(buf); i++)
-		if (!isgraph(buf[i])) buf[i] = ' ';   // bad chars -> spaces
+		if (!isgraph((int)buf[i])) buf[i] = ' ';   // bad chars -> spaces
 	return buf;
     }
 
diff --git a/tests/rigctl_parse.c b/tests/rigctl_parse.c
index c822f7272..3389b272a 100644
--- a/tests/rigctl_parse.c
+++ b/tests/rigctl_parse.c
@@ -724,7 +724,7 @@ int rigctl_parse(RIG *my_rig, FILE *fin, FILE *fout, char *argv[], int argc)
 			 * alpha-numeric characters and the underscore ('_') character.
 			 */
 			for (j = 0; cmd_name[j] != '\0'; j++) {
-				if (!(isalnum(cmd_name[j]) || cmd_name[j] == '_')) {
+				if (!(isalnum((int)cmd_name[j]) || cmd_name[j] == '_')) {
 					fprintf(stderr, "Valid multiple character command names contain alpha-numeric characters plus '_'\n");
 					return 0;
 				}
@@ -807,7 +807,7 @@ int rigctl_parse(RIG *my_rig, FILE *fin, FILE *fout, char *argv[], int argc)
 #endif
 			/* Sanity check, VFO names are alpha only. */
 			for (j = 0; j < MAXNAMSIZ && parsed_input[x][j] != '\0'; j++) {
-				if (!(isalpha(parsed_input[x][j]))) {
+				if (!(isalpha((int)parsed_input[x][j]))) {
 					parsed_input[x][j] = '\0';
 
 					break;
@@ -2106,7 +2106,7 @@ declare_proto_rig(set_channel)
 
 	memset(&chan, 0, sizeof(channel_t));
 
-	if (isdigit(arg1[0])) {
+	if (isdigit((int)arg1[0])) {
 		chan.vfo = RIG_VFO_MEM;
 		CHKSCN1ARG(sscanf(arg1, "%d", &chan.channel_num));
 		/*
@@ -2280,7 +2280,7 @@ declare_proto_rig(get_channel)
 
 	memset(&chan, 0, sizeof(channel_t));
 
-	if (isdigit(arg1[0])) {
+	if (isdigit((int)arg1[0])) {
 		chan.vfo = RIG_VFO_MEM;
 		CHKSCN1ARG(sscanf(arg1, "%d", &chan.channel_num));
 	} else {
diff --git a/tests/rotctl_parse.c b/tests/rotctl_parse.c
index 0d5dd558f..6b70af1dc 100644
--- a/tests/rotctl_parse.c
+++ b/tests/rotctl_parse.c
@@ -630,7 +630,7 @@ int rotctl_parse(ROT *my_rot, FILE *fin, FILE *fout, char *argv[], int argc)
 			 * alpha-numeric characters and the underscore ('_') character.
 			 */
 			for (j = 0; cmd_name[j] != '\0'; j++) {
-				if (!(isalnum(cmd_name[j]) || cmd_name[j] == '_')) {
+				if (!(isalnum((int)cmd_name[j]) || cmd_name[j] == '_')) {
 					fprintf(stderr, "Valid multiple character command names contain alpha-numeric characters plus '_'\n");
 					return 0;
 				}