diff --git a/debugfs/Makefile.in b/debugfs/Makefile.in
index 3dd06f03..574897ee 100644
--- a/debugfs/Makefile.in
+++ b/debugfs/Makefile.in
@@ -121,13 +121,22 @@ uninstall:
 
 clean::
 	$(RM) -f $(PROGS) debugfs.8 \#* *.s *.o *.a *~ debug_cmds.c \
-		extent_cmds.c ro_debug_cmds.c core rdebugfs debugfs.static
+		extent_cmds.c ro_debug_cmds.c core rdebugfs debugfs.static \
+		tst_set_fields
 
 mostlyclean: clean
 distclean: clean
 	$(RM) -f debug_cmds.c .depend Makefile $(srcdir)/TAGS \
 		$(srcdir)/Makefile.in.old
 
+tst_set_fields: set_fields.c util.c
+	$(E) "  LD $@"
+	$(Q) $(CC) $(ALL_CFLAGS) $(ALL_LDFLAGS) $(SYSLIBS) -DUNITTEST \
+		-o tst_set_fields $(srcdir)/set_fields.c $(srcdir)/util.c $(LIBS)
+
+check:: tst_set_fields
+	$(TESTENV) ./tst_set_fields
+
 # +++ Dependency line eater +++
 # 
 # Makefile dependencies follow.  This must be the last section in
diff --git a/debugfs/set_fields.c b/debugfs/set_fields.c
index 6104b2be..8297e089 100644
--- a/debugfs/set_fields.c
+++ b/debugfs/set_fields.c
@@ -30,6 +30,7 @@
 #ifdef HAVE_ERRNO_H
 #include <errno.h>
 #endif
+#include <assert.h>
 #if HAVE_STRINGS_H
 #include <strings.h>
 #endif
@@ -50,6 +51,7 @@ static ext2_ino_t set_ino;
 static int array_idx;
 
 #define FLAG_ARRAY	0x0001
+#define FLAG_ALIAS	0x0002	/* Data intersects with other field */
 
 struct field_set_info {
 	const char	*name;
@@ -110,7 +112,6 @@ static struct field_set_info super_fields[] = {
 	{ "uuid", &set_sb.s_uuid, NULL, 16, parse_uuid },
 	{ "volume_name",  &set_sb.s_volume_name, NULL, 16, parse_string },
 	{ "last_mounted",  &set_sb.s_last_mounted, NULL, 64, parse_string },
-	{ "lastcheck",  &set_sb.s_lastcheck, NULL, 4, parse_uint },
 	{ "algorithm_usage_bitmap", &set_sb.s_algorithm_usage_bitmap, NULL,
 		  4, parse_uint },
 	{ "prealloc_blocks", &set_sb.s_prealloc_blocks, NULL, 1, parse_uint },
@@ -135,7 +136,6 @@ static struct field_set_info super_fields[] = {
 	{ "want_extra_isize", &set_sb.s_want_extra_isize, NULL, 2, parse_uint },
 	{ "flags", &set_sb.s_flags, NULL, 4, parse_uint },
 	{ "raid_stride", &set_sb.s_raid_stride, NULL, 2, parse_uint },
-	{ "min_extra_isize", &set_sb.s_min_extra_isize, NULL, 4, parse_uint },
 	{ "mmp_interval", &set_sb.s_mmp_update_interval, NULL, 2, parse_uint },
 	{ "mmp_block", &set_sb.s_mmp_block, NULL, 8, parse_uint },
 	{ "raid_stripe_width", &set_sb.s_raid_stripe_width, NULL, 4, parse_uint },
@@ -158,17 +158,16 @@ static struct field_set_info super_fields[] = {
 	{ "first_error_ino", &set_sb.s_first_error_ino, NULL, 4, parse_uint },
 	{ "first_error_block", &set_sb.s_first_error_block, NULL, 8, parse_uint },
 	{ "first_error_func", &set_sb.s_first_error_func, NULL, 32, parse_string },
-	{ "first_error_line", &set_sb.s_first_error_ino, NULL, 4, parse_uint },
+	{ "first_error_line", &set_sb.s_first_error_line, NULL, 4, parse_uint },
 	{ "last_error_time", &set_sb.s_last_error_time, NULL, 4, parse_time },
 	{ "last_error_ino", &set_sb.s_last_error_ino, NULL, 4, parse_uint },
 	{ "last_error_block", &set_sb.s_last_error_block, NULL, 8, parse_uint },
 	{ "last_error_func", &set_sb.s_last_error_func, NULL, 32, parse_string },
-	{ "last_error_line", &set_sb.s_last_error_ino, NULL, 4, parse_uint },
+	{ "last_error_line", &set_sb.s_last_error_line, NULL, 4, parse_uint },
 	{ 0, 0, 0, 0 }
 };
 
 static struct field_set_info inode_fields[] = {
-	{ "inodes_count", &set_sb.s_inodes_count, NULL, 4, parse_uint },
 	{ "mode", &set_inode.i_mode, NULL, 2, parse_uint },
 	{ "uid", &set_inode.i_uid, &set_inode.osd2.linux2.l_i_uid_high,
 		2, parse_uint },
@@ -186,7 +185,8 @@ static struct field_set_info inode_fields[] = {
 	{ "flags", &set_inode.i_flags, NULL, 4, parse_uint },
 	{ "version", &set_inode.osd1.linux1.l_i_version,
 		&set_inode.i_version_hi, 4, parse_uint },
-	{ "translator", &set_inode.osd1.hurd1.h_i_translator, NULL, 4, parse_uint },
+	{ "translator", &set_inode.osd1.hurd1.h_i_translator, NULL,
+		4, parse_uint, FLAG_ALIAS },
 	{ "block", &set_inode.i_block[0], NULL, 4, parse_uint, FLAG_ARRAY,
 	  EXT2_NDIR_BLOCKS },
 	{ "block[IND]", &set_inode.i_block[EXT2_IND_BLOCK], NULL, 4, parse_uint },
@@ -196,14 +196,14 @@ static struct field_set_info inode_fields[] = {
 	/* Special case: i_file_acl_high is 2 bytes */
 	{ "file_acl", &set_inode.i_file_acl, 
 		&set_inode.osd2.linux2.l_i_file_acl_high, 6, parse_uint },
-	{ "dir_acl", &set_inode.i_dir_acl, NULL, 4, parse_uint },
+	{ "dir_acl", &set_inode.i_dir_acl, NULL, 4, parse_uint, FLAG_ALIAS },
 	{ "faddr", &set_inode.i_faddr, NULL, 4, parse_uint },
-	{ "frag", &set_inode.osd2.hurd2.h_i_frag, NULL, 1, parse_uint },
+	{ "frag", &set_inode.osd2.hurd2.h_i_frag, NULL, 1, parse_uint, FLAG_ALIAS },
 	{ "fsize", &set_inode.osd2.hurd2.h_i_fsize, NULL, 1, parse_uint },
 	{ "checksum", &set_inode.osd2.linux2.l_i_checksum_lo, 
 		&set_inode.i_checksum_hi, 2, parse_uint },
 	{ "author", &set_inode.osd2.hurd2.h_i_author, NULL,
-		4, parse_uint },
+		4, parse_uint, FLAG_ALIAS },
 	{ "extra_isize", &set_inode.i_extra_isize, NULL,
 		2, parse_uint },
 	{ "ctime_extra", &set_inode.i_ctime_extra, NULL,
@@ -259,7 +259,8 @@ static struct field_set_info ext4_bg_fields[] = {
 };
 
 static struct field_set_info mmp_fields[] = {
-	{ "clear", &set_mmp.mmp_magic, NULL, sizeof(set_mmp), parse_mmp_clear },
+	{ "clear", &set_mmp.mmp_magic, NULL, sizeof(set_mmp),
+		parse_mmp_clear, FLAG_ALIAS },
 	{ "magic", &set_mmp.mmp_magic, NULL, 4, parse_uint },
 	{ "seq", &set_mmp.mmp_seq, NULL, 4, parse_uint },
 	{ "time", &set_mmp.mmp_time, NULL, 8, parse_uint },
@@ -268,8 +269,60 @@ static struct field_set_info mmp_fields[] = {
 	{ "bdevname", &set_mmp.mmp_bdevname, NULL, sizeof(set_mmp.mmp_bdevname),
 		parse_string },
 	{ "check_interval", &set_mmp.mmp_check_interval, NULL, 2, parse_uint },
+	{ 0, 0, 0, 0 }
 };
 
+#ifdef UNITTEST
+
+static void do_verify_field_set_info(struct field_set_info *fields,
+		const void *data, size_t size)
+{
+	struct field_set_info *ss, *ss2;
+	const char *begin = (char *)data;
+	const char *end = begin + size;
+
+	for (ss = fields ; ss->name ; ss++) {
+		const char *ptr;
+
+		/* Check pointers */
+		ptr = ss->ptr;
+		assert(!ptr || (ptr >= begin && ptr < end));
+		ptr = ss->ptr2;
+		assert(!ptr || (ptr >= begin && ptr < end));
+
+		/* Check function */
+		assert(ss->func);
+
+		for (ss2 = fields ; ss2 != ss ; ss2++) {
+			/* Check duplicate names */
+			assert(strcmp(ss->name, ss2->name));
+
+			if (ss->flags & FLAG_ALIAS || ss2->flags & FLAG_ALIAS)
+				continue;
+			/* Check false aliases, might be copy-n-paste error */
+			assert(!ss->ptr || (ss->ptr != ss2->ptr &&
+					    ss->ptr != ss2->ptr2));
+			assert(!ss->ptr2 || (ss->ptr2 != ss2->ptr &&
+					     ss->ptr2 != ss2->ptr2));
+		}
+	}
+}
+
+int main(int argc, char **argv)
+{
+	do_verify_field_set_info(super_fields, &set_sb, sizeof(set_sb));
+	do_verify_field_set_info(inode_fields, &set_inode, sizeof(set_inode));
+	do_verify_field_set_info(ext2_bg_fields, &set_gd, sizeof(set_gd));
+	do_verify_field_set_info(ext4_bg_fields, &set_gd4, sizeof(set_gd4));
+	do_verify_field_set_info(mmp_fields, &set_mmp, sizeof(set_mmp));
+	return 0;
+}
+
+ext2_filsys current_fs;
+ext2_ino_t root, cwd;
+
+#endif /* UNITTEST */
+
 static int check_suffix(const char *field)
 {
 	int len = strlen(field);