diff --git a/sys/boot/zfs/zfs.c b/sys/boot/zfs/zfs.c
index c90e1c7..6b7f22f 100644
--- a/sys/boot/zfs/zfs.c
+++ b/sys/boot/zfs/zfs.c
@@ -90,8 +90,10 @@ zfs_open(const char *upath, struct open_file *f)
 	struct file *fp;
 	int rc;
 
+	printf("zfs_open: %s\n", upath);
 	if (f->f_dev != &zfs_dev && f->f_dev != &zfs_dev_compat)
 		return (EINVAL);
+	printf("using %s\n", f->f_dev == &zfs_dev ? "zfs_dev" : "zfs_dev_compat");
 
 	/* allocate file system specific data structure */
 	fp = malloc(sizeof(struct file));
@@ -99,6 +101,7 @@ zfs_open(const char *upath, struct open_file *f)
 	f->f_fsdata = (void *)fp;
 
 	rc = zfs_lookup(mount, upath, &fp->f_dnode);
+	printf("zfs_lookup returns %d\n", rc);
 	fp->f_seekp = 0;
 	if (rc) {
 		f->f_fsdata = NULL;
@@ -426,12 +429,14 @@ zfs_dev_open_spa(struct open_file *f, spa_t *spa, uint64_t root_guid)
 	rv = zfs_spa_init(spa);
 	if (rv != 0)
 		return (rv);
+	printf("pool initialized\n");
 	mount = malloc(sizeof(*mount));
 	rv = zfs_mount(spa, root_guid, mount);
 	if (rv != 0) {
 		free(mount);
 		return (rv);
 	}
+	printf("pool mounted\n");
 	if (mount->objset.os_type != DMU_OST_ZFS) {
 		printf("Unexpected object set type %llu\n",
 		    mount->objset.os_type);
@@ -476,9 +481,11 @@ zfs_dev_open_compat(struct open_file *f, ...)
 	dev = va_arg(args, struct devdesc *);
 	va_end(args);
 
+	printf("zfs_dev_open: unit = %d\n", dev->d_unit);
 	spa = spa_find_by_unit(dev->d_unit);
 	if (!spa)
 		return (ENXIO);
+	printf("... found pool %s\n", spa->spa_name);
 	rv = zfs_dev_open_spa(f, spa, 0);
 	if (rv != 0)
 		return (rv);
diff --git a/sys/boot/zfs/zfsimpl.c b/sys/boot/zfs/zfsimpl.c
index d4c85dd..b595912 100644
--- a/sys/boot/zfs/zfsimpl.c
+++ b/sys/boot/zfs/zfsimpl.c
@@ -673,7 +673,7 @@ zfs_guid_to_unit(uint64_t guid)
 		unit++;
 	}
 
-	return (0);
+	return (-1);
 }
 #endif
 
@@ -1929,18 +1929,22 @@ zfs_lookup(const struct zfsmount *mount, const char *upath, dnode_phys_t *dnode)
 	/*
 	 * Get the root directory dnode.
 	 */
+	printf("getting master dnode\n");
 	rc = objset_get_dnode(spa, &mount->objset, MASTER_NODE_OBJ, &dn);
 	if (rc)
 		return (rc);
 
+	printf("looking up root dataset id\n");
 	rc = zap_lookup(spa, &dn, ZFS_ROOT_OBJ, &rootnum);
 	if (rc)
 		return (rc);
 
+	printf("getting root dnode\n");
 	rc = objset_get_dnode(spa, &mount->objset, rootnum, &dn);
 	if (rc)
 		return (rc);
 
+	printf("starting search\n");
 	objnum = rootnum;
 	p = upath;
 	while (p && *p) {