--- b/sys/fs/unionfs/union_subr.c	
+++ b/sys/fs/unionfs/union_subr.c	
@@ -916,7 +916,11 @@ unionfs_mkshadowdir(struct unionfs_mount *ump, struct vnode *udvp,
 		goto unionfs_mkshadowdir_abort;
 	unionfs_create_uppervattr_core(ump, &lva, &va, td);
 
+	char *pathend = &nd.ni_cnd.cn_nameptr[nd.ni_cnd.cn_namelen];
+	char pathterm = *pathend;
+	*pathend = '\0';
 	error = VOP_MKDIR(udvp, &uvp, &nd.ni_cnd, &va);
+	*pathend = pathterm;
 
 	if (!error) {
 		unionfs_node_update(unp, uvp, td);