diff --git a/math/primecount/Makefile b/math/primecount/Makefile
index d736a2629c21..28d0d32c2d58 100644
--- a/math/primecount/Makefile
+++ b/math/primecount/Makefile
@@ -1,32 +1,36 @@
 PORTNAME=	primecount
 DISTVERSIONPREFIX=	v
 DISTVERSION=	7.4
 CATEGORIES=	math
 
 MAINTAINER=	thierry@FreeBSD.org
 COMMENT=	Fast prime counting function implementations
 WWW=		https://github.com/kimwalisch/primecount
 
 LICENSE=	BSD2CLAUSE
 
 BUILD_DEPENDS=	libdivide>0:math/libdivide
 LIB_DEPENDS=	libprimesieve.so:math/primesieve
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	kimwalisch
 
 USES=		cmake compiler:c++11-lang
 USE_LDCONFIG=	yes
 
 CMAKE_ON=	BUILD_SHARED_LIBS
 CMAKE_OFF=	BUILD_LIBPRIMESIEVE BUILD_STATIC_LIBS
 
+.if !exists(/usr/local/omp.h)
+CMAKE_OFF+=	WITH_OPENMP
+.endif
+
 PLIST_SUB=	VER=${PORTVERSION}
 
 do-test:
 	cd ${BUILD_WRKSRC} && \
 	${SETENV} ${CONFIGURE_ENV} ${CMAKE_BIN} ${CMAKE_ARGS} -DBUILD_TESTS:BOOL=ON ${CMAKE_SOURCE_PATH} && \
 	${SETENV} ${MAKE_ENV} ${MAKE_CMD} ${MAKE_ARGS} ${ALL_TARGET} && \
 	${SETENV} ${MAKE_ENV} ${MAKE_CMD} ${MAKE_ARGS} test
 
 .include <bsd.port.mk>