Index: sbin/fsck_ffs/pass5.c
===================================================================
--- sbin/fsck_ffs/pass5.c
+++ sbin/fsck_ffs/pass5.c
@@ -73,6 +73,7 @@
 	newcg->cg_niblk = fs->fs_ipg;
 	if (preen == 0 && yflag == 0 && fs->fs_magic == FS_UFS2_MAGIC &&
 	    fswritefd != -1 && (fs->fs_metackhash & CK_CYLGRP) == 0 &&
+	    getosreldate() >= FREEBSD_VERS_CYLGRP &&
 	    reply("ADD CYLINDER GROUP CHECKSUM PROTECTION") != 0) {
 		fs->fs_metackhash |= CK_CYLGRP;
 		rewritecg = 1;
Index: sbin/newfs/mkfs.c
===================================================================
--- sbin/newfs/mkfs.c
+++ sbin/newfs/mkfs.c
@@ -495,7 +495,7 @@
 	/*
 	 * Set flags for metadata that is being check-hashed.
 	 */
-	if (Oflag > 1)
+	if (Oflag > 1 && getosreldate() >= FREEBSD_VERS_CYLGRP)
 		sblock.fs_metackhash = CK_CYLGRP;
 
 	/*
Index: sbin/newfs/newfs.c
===================================================================
--- sbin/newfs/newfs.c
+++ sbin/newfs/newfs.c
@@ -398,10 +398,6 @@
 		if (pp != NULL)
 			pp->p_size *= secperblk;
 	}
-	if (getosreldate() < __FreeBSD_version) {
-		warnx("%s is newer than the running kernel and may not be compatible",
-		    getprogname());
-	}
 	mkfs(pp, special);
 	ufs_disk_close(&disk);
 	if (!jflag)
Index: sys/ufs/ffs/fs.h
===================================================================
--- sys/ufs/ffs/fs.h
+++ sys/ufs/ffs/fs.h
@@ -453,6 +453,9 @@
 #define	CK_INODE	0x0004	/* inodes */
 #define	CK_INDIR	0x0008	/* indirect blocks */
 #define	CK_DIR		0x0010	/* directory contents */
+
+#define FREEBSD_VERS_CYLGRP 1200046	/* First version with CK_CYLGRP */
+
 /*
  * The BX_FSPRIV buffer b_xflags are used to track types of data in buffers.
  */