diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index d7222a9..c1a3927 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -31,17 +31,7 @@
 #include <asm/div64.h>
 #include <asm/sections.h>	/* for dereference_function_descriptor() */
 
-static unsigned int simple_guess_base(const char *cp)
-{
-	if (cp[0] == '0') {
-		if (_tolower(cp[1]) == 'x' && isxdigit(cp[2]))
-			return 16;
-		else
-			return 8;
-	} else {
-		return 10;
-	}
-}
+#include "kstrtox.h"
 
 /**
  * simple_strtoull - convert a string to an unsigned long long
@@ -51,23 +41,14 @@
  */
 unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
 {
-	unsigned long long result = 0;
+	unsigned long long result;
+	unsigned int rv;
 
-	if (!base)
-		base = simple_guess_base(cp);
+	cp = _parse_integer_fixup_radix(cp, &base);
+	rv = _parse_integer(cp, base, &result);
+	/* FIXME */
+	cp += (rv & ~KSTRTOX_OVERFLOW);
 
-	if (base == 16 && cp[0] == '0' && _tolower(cp[1]) == 'x')
-		cp += 2;
-
-	while (isxdigit(*cp)) {
-		unsigned int value;
-
-		value = isdigit(*cp) ? *cp - '0' : _tolower(*cp) - 'a' + 10;
-		if (value >= base)
-			break;
-		result = result * base + value;
-		cp++;
-	}
 	if (endp)
 		*endp = (char *)cp;