--- pkgsrc-2017Q2/devel/boost-libs/Makefile	2017-07-15 13:10:14.090677457 +0200
+++ pkgsrc/devel/boost-libs/Makefile	2017-07-15 13:14:10.808046077 +0200
@@ -35,15 +35,15 @@
 # XXX boost1.64 fiber not building even on netbsd7.99 + gcc5.4
 # fiber requires context, so also disable it where context cannot be built
 # Additionally fiber checks std::timed_mutex.
-#.if ((${OPSYS} == "Darwin" && ${OS_VERSION:R} < 14) || \
-#    !empty(MACHINE_PLATFORM:MNetBSD-[0-7]*-*)) || \
-#    !empty(MACHINE_ARCH:Malpha) || !empty(MACHINE_ARCH:Mm68k) || \
-#    !empty(MACHINE_ARCH:Msparc64) || \
-#    (${OPSYS} == "NetBSD" && !empty(PKGSRC_COMPILER:Mclang))
+.if ((${OPSYS} == "Darwin" && ${OS_VERSION:R} < 14) || \
+    !empty(MACHINE_PLATFORM:MNetBSD-[0-7]*-*)) || \
+    !empty(MACHINE_ARCH:Malpha) || !empty(MACHINE_ARCH:Mm68k) || \
+    !empty(MACHINE_ARCH:Msparc64) || \
+    (${OPSYS} == "NetBSD" && !empty(PKGSRC_COMPILER:Mclang))
 BJAM_ARGS+=		--without-fiber
-#.else
-#PLIST.fiber=		yes
-#.endif
+.else
+PLIST.fiber=		yes
+.endif
 
 UNLIMIT_RESOURCES+=	stacksize