Index: head/share/man/man9/printf.9
===================================================================
--- head/share/man/man9/printf.9
+++ head/share/man/man9/printf.9
@@ -26,7 +26,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd November 18, 2015
+.Dd May 9, 2020
 .Dt PRINTF 9
 .Os
 .Sh NAME
@@ -83,7 +83,7 @@
 .Xr printf 3 .
 However,
 .Xr printf 9
-adds two other conversion specifiers.
+adds two other conversion specifiers and omits one.
 .Pp
 The
 .Cm \&%b
@@ -119,6 +119,10 @@
 The string is used as a delimiter between individual bytes.
 If present, a width directive will specify the number of bytes to display.
 By default, 16 bytes of data are output.
+.Pp
+The
+.Cm \&%n
+conversion specifier is not supported.
 .Pp
 The
 .Fn log
Index: head/sys/kern/subr_prf.c
===================================================================
--- head/sys/kern/subr_prf.c
+++ head/sys/kern/subr_prf.c
@@ -775,20 +775,24 @@
 				lflag = 1;
 			goto reswitch;
 		case 'n':
+			/*
+			 * We do not support %n in kernel, but consume the
+			 * argument.
+			 */
 			if (jflag)
-				*(va_arg(ap, intmax_t *)) = retval;
+				(void)va_arg(ap, intmax_t *);
 			else if (qflag)
-				*(va_arg(ap, quad_t *)) = retval;
+				(void)va_arg(ap, quad_t *);
 			else if (lflag)
-				*(va_arg(ap, long *)) = retval;
+				(void)va_arg(ap, long *);
 			else if (zflag)
-				*(va_arg(ap, size_t *)) = retval;
+				(void)va_arg(ap, size_t *);
 			else if (hflag)
-				*(va_arg(ap, short *)) = retval;
+				(void)va_arg(ap, short *);
 			else if (cflag)
-				*(va_arg(ap, char *)) = retval;
+				(void)va_arg(ap, char *);
 			else
-				*(va_arg(ap, int *)) = retval;
+				(void)va_arg(ap, int *);
 			break;
 		case 'o':
 			base = 8;