diff --git a/sys/include/string.h b/sys/include/string.h
index ffc5559..c0df22b 100644
--- a/sys/include/string.h
+++ b/sys/include/string.h
@@ -26,10 +26,14 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef _STRING_H
-#define _STRING_H
+#ifndef _STRING_H_
+#define _STRING_H_
 
-#include <sys/types.h>
+#include <sys/cdefs.h>
+#include <sys/_null.h>
+#include <sys/_types.h>
+
+
 #include <strings.h>
 
 void *memcpy(const void *dst, const void * src, size_t length);
@@ -44,9 +48,9 @@
 char *strtok_r(char *str, const char *sep, char **last);
 char *strstr(const char *s, char *find);
 
-extern u_char const bcd2bin_data[];
-extern u_char const bin2bcd_data[];
-extern char const hex2ascii_data[];
+extern const u_char bcd2bin_data[];
+extern const u_char bin2bcd_data[];
+extern const char hex2ascii_data[];
 
 #define bcd2bin(bcd)    (bcd2bin_data[bcd])
 #define bin2bcd(bin)    (bin2bcd_data[bin])
@@ -59,16 +63,10 @@
 extern "C" {
 #endif
 
-
-
-
-
-
-
   int sprintf(char *buf, const char *fmt, ...);
 
 #ifdef __cplusplus
 }
 #endif
 
-#endif /* END _STRING_H */
+#endif /* !_STRING_H_ */