diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index e994cea385c8..a900d136e643 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -381,8 +381,8 @@ static noinline char *put_dec(char *buf, unsigned long long num)
 #define PLUS	4		/* show plus */
 #define SPACE	8		/* space if plus */
 #define LEFT	16		/* left justified */
-#define SMALL	32		/* Must be 32 == 0x20 */
-#define SPECIAL	64		/* 0x */
+#define SMALL	32		/* use lowercase in hex (must be 32 == 0x20) */
+#define SPECIAL	64		/* prefix hex with "0x", octal with "0" */
 
 enum format_type {
 	FORMAT_TYPE_NONE, /* Just a string part */