diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 6438cd5..e5ab51f 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -546,12 +546,12 @@ static char *number(char *buf, char *end, unsigned long long num,
 	return buf;
 }
 
-static char *string(char *buf, char *end, char *s, struct printf_spec spec)
+static char *string(char *buf, char *end, const char *s, struct printf_spec spec)
 {
 	int len, i;
 
 	if ((unsigned long)s < PAGE_SIZE)
-		s = "<NULL>";
+		s = "(null)";
 
 	len = strnlen(s, spec.precision);
 
@@ -1498,7 +1498,7 @@ do {									\
 			size_t len;
 			if ((unsigned long)save_str > (unsigned long)-PAGE_SIZE
 					|| (unsigned long)save_str < PAGE_SIZE)
-				save_str = "<NULL>";
+				save_str = "(null)";
 			len = strlen(save_str);
 			if (str + len + 1 < end)
 				memcpy(str, save_str, len + 1);