diff --git a/sbin/fsck/fsck.c b/sbin/fsck/fsck.c
index b483a9bb3bba..35a4b91d64f6 100644
--- a/sbin/fsck/fsck.c
+++ b/sbin/fsck/fsck.c
@@ -278,7 +278,7 @@ isok(struct fstab *fs)
 
 
 static int
-checkfs(const char *vfstype, const char *spec, const char *mntpt,
+checkfs(const char *pvfstype, const char *spec, const char *mntpt,
     char *auxopt, pid_t *pidp)
 {
 	/* List of directories containing fsck_xxx subcommands. */
@@ -291,6 +291,7 @@ checkfs(const char *vfstype, const char *spec, const char *mntpt,
 	pid_t pid;
 	int argc, i, status, maxargc;
 	char *optbuf, execname[MAXPATHLEN + 1], execbase[MAXPATHLEN];
+	char *vfstype = NULL;
 	const char *extra = NULL;
 
 #ifdef __GNUC__
@@ -298,6 +299,24 @@ checkfs(const char *vfstype, const char *spec, const char *mntpt,
 	(void) &optbuf;
 	(void) &vfstype;
 #endif
+	/*
+	 * We convert the vfstype to lowercase and any spaces to underscores
+	 * to not confuse the issue
+	 *
+	 * XXX This is a kludge to make automatic filesystem type guessing
+	 * from the disklabel work for "4.2BSD" filesystems.  It does a
+	 * very limited subset of transliteration to a normalised form of
+	 * filesystem name, and we do not seem to enforce a filesystem
+	 * name character set.
+	 */
+	vfstype = strdup(pvfstype);
+	if (vfstype == NULL)
+		perror("strdup(pvfstype)"); 
+	for (i = 0; i < strlen(vfstype); i++) {
+		vfstype[i] = tolower(vfstype[i]);
+		if (vfstype[i] == ' ')
+			vfstype[i] = '_';
+	}
 
 	extra = getoptions(vfstype);
 	optbuf = NULL;
@@ -334,6 +353,7 @@ checkfs(const char *vfstype, const char *spec, const char *mntpt,
 		warn("vfork");
 		if (optbuf)
 			free(optbuf);
+		free(vfstype);
 		return (1);
 
 	case 0:					/* Child. */
@@ -367,6 +387,8 @@ checkfs(const char *vfstype, const char *spec, const char *mntpt,
 		if (optbuf)
 			free(optbuf);
 
+		free(vfstype);
+
 		if (pidp) {
 			*pidp = pid;
 			return 0;