diff --git a/devel/qjson/Makefile b/devel/qjson/Makefile
--- a/devel/qjson/Makefile
+++ b/devel/qjson/Makefile
@@ -29,12 +29,6 @@
 
 DOXYGEN_BUILD_DEPENDS=	doxygen:devel/doxygen
 
-.include <bsd.port.options.mk>
-
-.if ${OPSYS} == FreeBSD && ${OSVERSION} >= 1400091
-CXXFLAGS+=  -Dregister=
-.endif
-
 post-build-DOXYGEN-on:
 	cd ${WRKSRC}/doc && doxygen
 
@@ -42,4 +36,12 @@
 	${MKDIR} ${STAGEDIR}${_DOCSDIR}
 	cd ${WRKSRC}/doc/html && ${COPYTREE_SHARE} . ${STAGEDIR}${_DOCSDIR}
 
-.include <bsd.port.mk>
+.include <bsd.port.pre.mk>
+
+# Clang 16 defaults to building in C++17, and throws an error when the
+# `register' keyword is used. Make clang just ignore the keyword instead.
+.if ${COMPILER_TYPE} == clang && ${COMPILER_VERSION} >= 160
+CXXFLAGS+=	-Wno-register
+.endif
+
+.include <bsd.port.post.mk>