--- OLD/popt/poptparse.c	Thu Jan  1 00:00:00 1970
+++ NEW/popt/poptparse.c	Thu Jan  1 00:00:00 1970
@@ -78,7 +78,7 @@
 		if (*src != quote) *buf++ = '\\';
 	    }
 	    *buf++ = *src;
-	} else if (isspace(*src)) {
+	} else if (isspace((unsigned char)*src)) {
 	    if (*argv[argc] != '\0') {
 		buf++, argc++;
 		if (argc == argvAlloced) {