diff --git a/sbin/fsck_ffs/dir.c b/sbin/fsck_ffs/dir.c
index 9203000f4fce..604349779c4e 100644
--- a/sbin/fsck_ffs/dir.c
+++ b/sbin/fsck_ffs/dir.c
@@ -702,7 +702,7 @@ static struct bufarea *
 getdirblk(ufs2_daddr_t blkno, long size)
 {
 
-	if (pdirbp != 0)
+	if (pdirbp != NULL)
 		pdirbp->b_flags &= ~B_INUSE;
 	pdirbp = getdatablk(blkno, size, BT_DIRDATA);
 	return (pdirbp);
diff --git a/sbin/fsck_ffs/fsutil.c b/sbin/fsck_ffs/fsutil.c
index bc80e2f3e322..713c9d4a168e 100644
--- a/sbin/fsck_ffs/fsutil.c
+++ b/sbin/fsck_ffs/fsutil.c
@@ -184,7 +184,7 @@ bufinit(void)
 
 	pbp = pdirbp = (struct bufarea *)0;
 	bufp = Malloc((unsigned int)sblock.fs_bsize);
-	if (bufp == 0)
+	if (bufp == NULL)
 		errx(EEXIT, "cannot allocate buffer pool");
 	cgblk.b_un.b_buf = bufp;
 	initbarea(&cgblk, BT_CYLGRP);
diff --git a/sbin/fsck_ffs/inode.c b/sbin/fsck_ffs/inode.c
index e8baf097c22f..e93817834825 100644
--- a/sbin/fsck_ffs/inode.c
+++ b/sbin/fsck_ffs/inode.c
@@ -290,7 +290,7 @@ ginode(ino_t inumber)
 	if (startinum == 0 ||
 	    inumber < startinum || inumber >= startinum + INOPB(&sblock)) {
 		iblk = ino_to_fsba(&sblock, inumber);
-		if (pbp != 0)
+		if (pbp != NULL)
 			pbp->b_flags &= ~B_INUSE;
 		pbp = getdatablk(iblk, sblock.fs_bsize, BT_INODES);
 		startinum = (inumber / INOPB(&sblock)) * INOPB(&sblock);
@@ -608,7 +608,7 @@ pinode(ino_t ino)
 		return;
 	dp = ginode(ino);
 	printf(" OWNER=");
-	if ((pw = getpwuid((int)DIP(dp, di_uid))) != 0)
+	if ((pw = getpwuid((int)DIP(dp, di_uid))) != NULL)
 		printf("%s ", pw->pw_name);
 	else
 		printf("%u ", (unsigned)DIP(dp, di_uid));
diff --git a/sbin/fsck_ffs/main.c b/sbin/fsck_ffs/main.c
index 08c7745727e4..f2fb588f748f 100644
--- a/sbin/fsck_ffs/main.c
+++ b/sbin/fsck_ffs/main.c
@@ -349,10 +349,10 @@ checkfilesys(char *filesys)
 					pfatal(
 	"CANNOT FIND SNAPSHOT DIRECTORY %s: %s, CANNOT RUN IN BACKGROUND\n",
 					    snapname, strerror(errno));
-				} else if ((grp = getgrnam("operator")) == 0 ||
-				    mkdir(snapname, 0770) < 0 ||
-				    chown(snapname, -1, grp->gr_gid) < 0 ||
-				    chmod(snapname, 0770) < 0) {
+				} else if ((grp = getgrnam("operator")) == NULL ||
+					   mkdir(snapname, 0770) < 0 ||
+					   chown(snapname, -1, grp->gr_gid) < 0 ||
+					   chmod(snapname, 0770) < 0) {
 					bkgrdflag = 0;
 					pfatal(
 	"CANNOT CREATE SNAPSHOT DIRECTORY %s: %s, CANNOT RUN IN BACKGROUND\n",
diff --git a/sbin/fsck_ffs/pass1.c b/sbin/fsck_ffs/pass1.c
index 67fba6eaa35c..98d2a0552708 100644
--- a/sbin/fsck_ffs/pass1.c
+++ b/sbin/fsck_ffs/pass1.c
@@ -151,7 +151,7 @@ pass1(void)
 		 */
 		inostathead[c].il_numalloced = inosused;
 		if (inosused == 0) {
-			inostathead[c].il_stat = 0;
+			inostathead[c].il_stat = NULL;
 			continue;
 		}
 		info = Calloc((unsigned)inosused, sizeof(struct inostat));
@@ -221,7 +221,7 @@ pass1(void)
 		inostathead[c].il_numalloced = inosused;
 		if (inosused == 0) {
 			free(inostathead[c].il_stat);
-			inostathead[c].il_stat = 0;
+			inostathead[c].il_stat = NULL;
 			continue;
 		}
 		info = Calloc((unsigned)inosused, sizeof(struct inostat));
@@ -500,9 +500,9 @@ pass1check(struct inodesc *idesc)
 				return (STOP);
 			}
 			new->dup = blkno;
-			if (muldup == 0) {
+			if (muldup == NULL) {
 				duplist = muldup = new;
-				new->next = 0;
+				new->next = NULL;
 			} else {
 				new->next = muldup->next;
 				muldup->next = new;
diff --git a/sbin/fsck_ffs/pass1b.c b/sbin/fsck_ffs/pass1b.c
index 69a23c207ecd..52f74792c049 100644
--- a/sbin/fsck_ffs/pass1b.c
+++ b/sbin/fsck_ffs/pass1b.c
@@ -108,7 +108,7 @@ pass1bcheck(struct inodesc *idesc)
 			if (dlp == muldup)
 				break;
 		}
-		if (muldup == 0 || duphead == muldup->next) {
+		if (muldup == NULL || duphead == muldup->next) {
 			rerun = 1;
 			return (STOP);
 		}
diff --git a/sbin/fsck_ffs/pass4.c b/sbin/fsck_ffs/pass4.c
index 80a32c14b14c..3b64dfbaf537 100644
--- a/sbin/fsck_ffs/pass4.c
+++ b/sbin/fsck_ffs/pass4.c
@@ -143,7 +143,7 @@ pass4check(struct inodesc *idesc)
 				free((char *)dlp);
 				break;
 			}
-			if (dlp == 0) {
+			if (dlp == NULL) {
 				clrbmap(blkno);
 				n_blks--;
 			}
diff --git a/sbin/fsck_ffs/pass5.c b/sbin/fsck_ffs/pass5.c
index 13ef86dc548f..67ad68a71ef0 100644
--- a/sbin/fsck_ffs/pass5.c
+++ b/sbin/fsck_ffs/pass5.c
@@ -82,7 +82,7 @@ pass5(void)
 			}
 		}
 		if (fs->fs_maxcontig > 1) {
-			const char *doit = 0;
+			const char *doit = NULL;
 
 			if (fs->fs_contigsumsize < 1) {
 				doit = "CREAT";
diff --git a/sbin/fsck_ffs/utilities.c b/sbin/fsck_ffs/utilities.c
index 4e82c31640da..1a78cfda91ee 100644
--- a/sbin/fsck_ffs/utilities.c
+++ b/sbin/fsck_ffs/utilities.c
@@ -68,7 +68,7 @@ blockcheck(char *origname)
 	newname = origname;
 	if (stat(newname, &stblock) < 0) {
 		cp = strrchr(newname, '/');
-		if (cp == 0) {
+		if (cp == NULL) {
 			(void)snprintf(device, sizeof(device), "%s%s",
 				_PATH_DEV, newname);
 			newname = device;