--- devel/boost-all/compiled.mk.orig	2013-02-04 11:22:08.525015918 +0800
+++ devel/boost-all/compiled.mk.orig	2013-02-04 13:19:38.019015963 +0800
@@ -9,7 +9,7 @@ 
 PKG_MESSAGE_FILE_THREADS=	${PORTSDIR}/devel/boost-all/pkg-message.threads
 PKG_MESSAGE_FILE_PYTHON=	${PORTSDIR}/devel/boost-all/pkg-message.python
 
-BJAM_ARGS+=	--layout=system \
+BJAM_ARGS=	--layout=system \
 		--prefix=${PREFIX}
 
 .if ${ARCH} == amd64