diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index 168aea861637..ad944e5b8ea2 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -867,11 +867,11 @@ dsl_dataset_namelen(dsl_dataset_t *ds)
 	VERIFY0(dsl_dataset_get_snapname(ds));
 	mutex_enter(&ds->ds_lock);
 	int len = strlen(ds->ds_snapname);
+	mutex_exit(&ds->ds_lock);
 	/* add '@' if ds is a snap */
 	if (len > 0)
 		len++;
 	len += dsl_dir_namelen(ds->ds_dir);
-	mutex_exit(&ds->ds_lock);
 	return (len);
 }