diff --git a/cad/nvc/Makefile b/cad/nvc/Makefile
index dabd5ad8f1bc..29ae67564c65 100644
--- a/cad/nvc/Makefile
+++ b/cad/nvc/Makefile
@@ -1,37 +1,40 @@
 PORTNAME=	nvc
 DISTVERSIONPREFIX=	r
 DISTVERSION=	1.6.2
 PORTREVISION=	1
 CATEGORIES=	cad
 
 MAINTAINER=	yuri@FreeBSD.org
 COMMENT=	VHDL compiler and simulator
 
 LICENSE=	GPLv3
 LICENSE_FILE=	${WRKSRC}/COPYING
 
 BUILD_DEPENDS=	llvm-config${LLVM_VERSION}:devel/llvm${LLVM_VERSION}
 RUN_DEPENDS=	llvm${LLVM_VERSION}>0:devel/llvm${LLVM_VERSION}
 TEST_DEPENDS=	check>0:devel/check
+.if !exists(/usr/include/unwind.h)
+LIB_DEPENDS=	libunwind.so:devel/libunwind
+.endif
 
 USES=		autoreconf compiler:c++14-lang localbase pkgconfig
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	nickg
 
 GNU_CONFIGURE=	yes
 
 LDFLAGS+=	-lexecinfo
 
 CONFIGURE_ARGS=	--with-llvm=${LOCALBASE}/bin/llvm-config${LLVM_VERSION}
 
 TEST_TARGET=	check # one test fails
 
 MAKE_ARGS=	CFLAGS="${CFLAGS}" # only for tests
 
 LLVM_VERSION=	${LLVM_DEFAULT}
 
 post-install:
 	${FIND} ${STAGEDIR}${PREFIX} -name "*.so" | ${XARGS} ${STRIP_CMD}
 
 .include <bsd.port.mk>