diff --git a/devel/marl/Makefile b/devel/marl/Makefile
index 48c1469ffe3d..60ff905dd8a3 100644
--- a/devel/marl/Makefile
+++ b/devel/marl/Makefile
@@ -1,22 +1,25 @@
 PORTNAME=	marl
 PORTVERSION=	g20210818
 CATEGORIES=	devel
 
 MAINTAINER=	yuri@FreeBSD.org
 COMMENT=	Hybrid thread / fiber task scheduler written in C++11
 
 LICENSE=	APACHE20
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
+NOT_FOR_ARCHS=	riscv64
+NOT_FOR_ARCHS_REASON=	assembly isn't implemented, see src/osfiber_asm.h
+
 USES=		cmake:testing compiler:c++11-lang
 USE_LDCONFIG=	yes
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	google
 GH_TAGNAME=	4960243
 GH_TUPLE=	google:googletest:fb49e6c:googletest/third_party/googletest
 
 CMAKE_ON=	MARL_BUILD_SHARED MARL_INSTALL
 CMAKE_TESTING_ON=	MARL_BUILD_TESTS MARL_BUILD_EXAMPLES # tests are built but not run, see https://github.com/google/marl/issues/205
 
 .include <bsd.port.mk>