Index: head/math/py-ssm/Makefile
===================================================================
--- head/math/py-ssm/Makefile	(revision 552176)
+++ head/math/py-ssm/Makefile	(revision 552177)
@@ -1,32 +1,32 @@
 # $FreeBSD$
 
 PORTNAME=	ssm
 DISTVERSION=	0.0.1
 CATEGORIES=	math python
 MASTER_SITES=	CHEESESHOP
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}
 
 MAINTAINER=	yuri@FreeBSD.org
 COMMENT=	Bayesian learning and inference for state space models
 
 LICENSE=	MIT
 
 PY_DEPENDS=	${PYNUMPY} \
 		${PYTHON_PKGNAMEPREFIX}autograd>0:math/py-autograd@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}future>0:devel/py-future@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}matplotlib>0:math/py-matplotlib@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}numba>0:devel/py-numba@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}scipy>0:science/py-scipy@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}scikit-learn>0:science/py-scikit-learn@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}seaborn>0:math/py-seaborn@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}tqdm>0:misc/py-tqdm@${PY_FLAVOR}
 BUILD_DEPENDS=	${PY_DEPENDS}
 RUN_DEPENDS=	${PY_DEPENDS}
 
-USES=		python
+USES=		python:3.6+
 USE_PYTHON=	distutils cython concurrent autoplist
 
 post-install:
 	${STRIP_CMD} ${STAGEDIR}${PYTHONPREFIX_SITELIBDIR}/${PORTNAME}/*.so
 
 .include <bsd.port.mk>