diff --git a/runtime/tools/ccfilter.c b/runtime/tools/ccfilter.c
index 43489f1..ae1443e 100644
--- a/runtime/tools/ccfilter.c
+++ b/runtime/tools/ccfilter.c
@@ -249,7 +249,7 @@
 
 	    stay = (echogets(Line2, echo) != NULL);
 	    while ( stay && (Line2[0] == '|') )
-	      { for (p=&Line2[2]; (*p) && (isspace(*p)); p++);
+	      { for (p=&Line2[2]; (*p) && (isspace((unsigned char)*p)); p++);
 		strcat( Reason, ": " );
 		strcat( Reason, p );
 		Line2[0] = 0;
@@ -265,7 +265,7 @@
 	    ok	      = 0;
 	    if ( !strncmp(Line, "cfe: ", 5) )
 	      { p = &Line[5];
-		Severity = tolower(*p);
+		Severity = tolower((unsigned char)*p);
 		p = strchr( &Line[5], ':' );
 		if (p == NULL)
 		  { ok = 0;
@@ -313,7 +313,7 @@
 	}
        else
 	{
-	  for (p=Reason; (*p) && (isspace(*p)); p++);
+	  for (p=Reason; (*p) && (isspace((unsigned char)*p)); p++);
 	  if ( BasePath[CWDlen] == 0 )
 	      printf( "%s:%lu:%lu:%c:%s\n", FileName, Row, Col, Severity, p );
 	  else
diff --git a/runtime/tools/xcmdsrv_client.c b/runtime/tools/xcmdsrv_client.c
index e1aea10..81ca66c 100644
--- a/runtime/tools/xcmdsrv_client.c
+++ b/runtime/tools/xcmdsrv_client.c
@@ -336,7 +336,7 @@
     for (p = regProp; (p - regProp) < numItems; )
     {
 	entry = p;
-	while ((*p != 0) && (!isspace(*p)))
+	while ((*p != 0) && (!isspace((unsigned char)*p)))
 	    p++;
 	if ((*p != 0) && (strcasecmp(name, p + 1) == 0))
 	{
@@ -353,7 +353,7 @@
 	for (p = regProp; (p - regProp) < numItems; )
 	{
 	    entry = p;
-	    while ((*p != 0) && (!isspace(*p)))
+	    while ((*p != 0) && (!isspace((unsigned char)*p)))
 		p++;
 	    if ((*p != 0) && IsSerialName(p + 1)
 		    && (strncmp(name, p + 1, strlen(name)) == 0))
@@ -574,5 +574,5 @@
 {
     int len = strlen(str);
 
-    return (len > 1 && isdigit(str[len - 1]));
+    return (len > 1 && isdigit((unsigned char)str[len - 1]));
 }