diff --git a/appl/ftp/ftp/domacro.c b/appl/ftp/ftp/domacro.c
index 51651208e..ba518c3a4 100644
--- a/appl/ftp/ftp/domacro.c
+++ b/appl/ftp/ftp/domacro.c
@@ -60,7 +60,7 @@ domacro(int argc, char **argv)
 TOP:
 	cp1 = macros[i].mac_start;
 	while (cp1 != macros[i].mac_end) {
-		while (isspace(*cp1)) {
+		while (isspace((unsigned char)*cp1)) {
 			cp1++;
 		}
 		cp2 = line;
@@ -70,9 +70,9 @@ TOP:
 				 *cp2++ = *++cp1;
 				 break;
 			    case '$':
-				 if (isdigit(*(cp1+1))) {
+				 if (isdigit((unsigned char)*(cp1+1))) {
 				    j = 0;
-				    while (isdigit(*++cp1)) {
+				    while (isdigit((unsigned char)*++cp1)) {
 					  j = 10*j +  *cp1 - '0';
 				    }
 				    cp1--;
diff --git a/appl/telnet/telnet/commands.c b/appl/telnet/telnet/commands.c
index c0fd513f6..ca1138d7d 100644
--- a/appl/telnet/telnet/commands.c
+++ b/appl/telnet/telnet/commands.c
@@ -74,7 +74,7 @@ makeargv()
     }
     while ((c = *cp)) {
 	int inquote = 0;
-	while (isspace(c))
+	while (isspace((unsigned char)c))
 	    c = *++cp;
 	if (c == '\0')
 	    break;
@@ -96,7 +96,7 @@ makeargv()
 		} else if (c == '\'') {
 		    inquote = '\'';
 		    continue;
-		} else if (isspace(c))
+		} else if (isspace((unsigned char)c))
 		    break;
 	    }
 	    *cp2++ = c;
@@ -2026,11 +2026,11 @@ cmdrc(char *m1, char *m2)
 	if (line[0] == '#')
 	    continue;
 	if (gotmachine) {
-	    if (!isspace(line[0]))
+	    if (!isspace((unsigned char)line[0]))
 		gotmachine = 0;
 	}
 	if (gotmachine == 0) {
-	    if (isspace(line[0]))
+	    if (isspace((unsigned char)line[0]))
 		continue;
 	    if (strncasecmp(line, m1, l1) == 0)
 		strncpy(line, &line[l1], sizeof(line) - l1);