Index: head/lib/libc/sys/clock_gettime.2
===================================================================
--- head/lib/libc/sys/clock_gettime.2
+++ head/lib/libc/sys/clock_gettime.2
@@ -29,7 +29,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 20, 2015
+.Dd December 27, 2015
 .Dt CLOCK_GETTIME 2
 .Os
 .Sh NAME
@@ -134,6 +134,8 @@
 .It Bq Er EINVAL
 The
 .Fa clock_id
+or
+.Fa timespec
 argument
 was not a valid value.
 .It Bq Er EPERM
Index: head/lib/libc/sys/gettimeofday.2
===================================================================
--- head/lib/libc/sys/gettimeofday.2
+++ head/lib/libc/sys/gettimeofday.2
@@ -28,7 +28,7 @@
 .\"     @(#)gettimeofday.2	8.2 (Berkeley) 5/26/95
 .\" $FreeBSD$
 .\"
-.Dd December 20, 2015
+.Dd December 27, 2015
 .Dt GETTIMEOFDAY 2
 .Os
 .Sh NAME
@@ -110,6 +110,10 @@
 The following error codes may be set in
 .Va errno :
 .Bl -tag -width Er
+.It Bq Er EINVAL
+The supplied
+.Fa timeval
+value is invalid.
 .It Bq Er EPERM
 A user other than the super-user attempted to set the time.
 .El
Index: head/sys/kern/kern_time.c
===================================================================
--- head/sys/kern/kern_time.c
+++ head/sys/kern/kern_time.c
@@ -398,7 +398,8 @@
 		return (error);
 	if (clock_id != CLOCK_REALTIME)
 		return (EINVAL);
-	if (ats->tv_nsec < 0 || ats->tv_nsec >= 1000000000)
+	if (ats->tv_nsec < 0 || ats->tv_nsec >= 1000000000 ||
+	    ats->tv_sec < 0)
 		return (EINVAL);
 	/* XXX Don't convert nsec->usec and back */
 	TIMESPEC_TO_TIMEVAL(&atv, ats);
@@ -618,7 +619,8 @@
 		return (error);
 	/* Verify all parameters before changing time. */
 	if (tv) {
-		if (tv->tv_usec < 0 || tv->tv_usec >= 1000000)
+		if (tv->tv_usec < 0 || tv->tv_usec >= 1000000 ||
+		    tv->tv_sec < 0)
 			return (EINVAL);
 		error = settime(td, tv);
 	}