diff --git a/gnu/usr.bin/diff/system.h b/gnu/usr.bin/diff/system.h
index 47db2870e343..e15a9f08bc9f 100644
--- a/gnu/usr.bin/diff/system.h
+++ b/gnu/usr.bin/diff/system.h
@@ -190,20 +190,20 @@ void *memchr ();
 #if STDC_HEADERS
 #define CTYPE_DOMAIN(c) 1
 #else
-#define CTYPE_DOMAIN(c) ((unsigned) (c) <= 0177)
+#define CTYPE_DOMAIN(c) ((unsigned char) (c) <= 0177)
 #endif
 #ifndef ISPRINT
-#define ISPRINT(c) (CTYPE_DOMAIN (c) && isprint (c))
+#define ISPRINT(c) (CTYPE_DOMAIN (c) && isprint ((unsigned char)c))
 #endif
 #ifndef ISSPACE
-#define ISSPACE(c) (CTYPE_DOMAIN (c) && isspace (c))
+#define ISSPACE(c) (CTYPE_DOMAIN (c) && isspace ((unsigned char)c))
 #endif
 #ifndef ISUPPER
-#define ISUPPER(c) (CTYPE_DOMAIN (c) && isupper (c))
+#define ISUPPER(c) (CTYPE_DOMAIN (c) && isupper ((unsigned char)c))
 #endif
 
 #ifndef ISDIGIT
-#define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
+#define ISDIGIT(c) ((unsigned char) (c) - '0' <= 9)
 #endif
 
 #include <errno.h>
diff --git a/gnu/usr.bin/sort/system.h b/gnu/usr.bin/sort/system.h
index bfb19e121c34..ed0b26b0dbc5 100644
--- a/gnu/usr.bin/sort/system.h
+++ b/gnu/usr.bin/sort/system.h
@@ -167,30 +167,30 @@ char *getenv ();
 #if defined (STDC_HEADERS) || (!defined (isascii) && !defined (HAVE_ISASCII))
 #define ISASCII(c) 1
 #else
-#define ISASCII(c) isascii(c)
+#define ISASCII(c) isascii((unsigned char)c)
 #endif
 
 #ifdef isblank
-#define ISBLANK(c) (ISASCII (c) && isblank (c))
+#define ISBLANK(c) (ISASCII (c) && isblank ((unsigned char)c))
 #else
 #define ISBLANK(c) ((c) == ' ' || (c) == '\t')
 #endif
 #ifdef isgraph
-#define ISGRAPH(c) (ISASCII (c) && isgraph (c))
+#define ISGRAPH(c) (ISASCII (c) && isgraph ((unsigned char)c))
 #else
-#define ISGRAPH(c) (ISASCII (c) && isprint (c) && !isspace (c))
+#define ISGRAPH(c) (ISASCII (c) && isprint ((unsigned char)c) && !isspace ((unsigned char)c))
 #endif
 
-#define ISPRINT(c) (ISASCII (c) && isprint (c))
-#define ISDIGIT(c) (ISASCII (c) && isdigit (c))
-#define ISALNUM(c) (ISASCII (c) && isalnum (c))
-#define ISALPHA(c) (ISASCII (c) && isalpha (c))
-#define ISCNTRL(c) (ISASCII (c) && iscntrl (c))
-#define ISLOWER(c) (ISASCII (c) && islower (c))
-#define ISPUNCT(c) (ISASCII (c) && ispunct (c))
-#define ISSPACE(c) (ISASCII (c) && isspace (c))
-#define ISUPPER(c) (ISASCII (c) && isupper (c))
-#define ISXDIGIT(c) (ISASCII (c) && isxdigit (c))
+#define ISPRINT(c) (ISASCII (c) && isprint ((unsigned char)c))
+#define ISDIGIT(c) (ISASCII (c) && isdigit ((unsigned char)c))
+#define ISALNUM(c) (ISASCII (c) && isalnum ((unsigned char)c))
+#define ISALPHA(c) (ISASCII (c) && isalpha ((unsigned char)c))
+#define ISCNTRL(c) (ISASCII (c) && iscntrl ((unsigned char)c))
+#define ISLOWER(c) (ISASCII (c) && islower ((unsigned char)c))
+#define ISPUNCT(c) (ISASCII (c) && ispunct ((unsigned char)c))
+#define ISSPACE(c) (ISASCII (c) && isspace ((unsigned char)c))
+#define ISUPPER(c) (ISASCII (c) && isupper ((unsigned char)c))
+#define ISXDIGIT(c) (ISASCII (c) && isxdigit ((unsigned char)c))
 
 /* Disable string localization for the time being.  */
 #undef _