Index: devel/py-nbformat/Makefile
===================================================================
--- devel/py-nbformat/Makefile	(revision 460226)
+++ devel/py-nbformat/Makefile	(working copy)
@@ -2,6 +2,7 @@
 
 PORTNAME=	nbformat
 PORTVERSION=	4.4.0
+PORTREVISION=	1
 CATEGORIES=	devel python
 MASTER_SITES=	CHEESESHOP
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}
@@ -22,7 +23,7 @@
 
 NO_ARCH=	yes
 USES=		python
-USE_PYTHON=	autoplist distutils
+USE_PYTHON=	autoplist concurrent distutils
 
 do-test:
 	@(cd ${TEST_WRKSRC} && ${SETENV} ${TEST_ENV} pytest-${PYTHON_VER})