diff --git a/rtl837x_common.h b/rtl837x_common.h
index a00411c..731c3ec 100644
--- a/rtl837x_common.h
+++ b/rtl837x_common.h
@@ -2,6 +2,7 @@
 #define _RTL837X_STDIO_H_
 
 #include "uip/uip-conf.h"
+#include <stdint.h>
 
 // The serial buffer. Defines the command line size
 // Must be 2^x and <= 128
@@ -59,7 +60,7 @@ void memcpyc(register __xdata uint8_t *dst, register __code uint8_t *src, regist
 void memset(register __xdata uint8_t *dst, register __xdata uint8_t v, register uint8_t len);
 uint16_t strlen(register __code const char *s);
 uint16_t strlen_x(register __xdata const char *s);
-void strtox(register __xdata uint8_t *dst, register __code const char *s);
+uint16_t strtox(register __xdata uint8_t *dst, register __code const char *s);
 void tcpip_output(void);
 void print_string_x(__xdata char *p);
 
diff --git a/rtlplayground.c b/rtlplayground.c
index 29f07f2..cf81eff 100644
--- a/rtlplayground.c
+++ b/rtlplayground.c
@@ -165,11 +165,13 @@ void memset(register __xdata uint8_t *dst, register __xdata uint8_t v, register
 		*dst++ = v;
 }
 
-void strtox(register __xdata uint8_t *dst, register __code const char *s)
+uint16_t strtox(register __xdata uint8_t *dst, register __code const char *s)
 {
+	__xdata uint8_t *b = dst;
 	while (*s)
 		*dst++ = *s++;
 	*dst = 0;
+	return dst - b;
 }
 
 uint16_t strlen(register __code const char *s)