diff --git a/astro/gpstk/Makefile b/astro/gpstk/Makefile
index 8c1506c0d2c3..cdbf52adc14d 100644
--- a/astro/gpstk/Makefile
+++ b/astro/gpstk/Makefile
@@ -12,21 +12,22 @@ LICENSE_COMB=	multi
 
 USES=		cmake compiler:c++11-lang
 USE_CXXSTD=	c++14
-USE_LDCONFIG=	yes
-
 USE_GITHUB=	yes
 GH_ACCOUNT=	SGL-UT
 GH_PROJECT=	GPSTk
+USE_LDCONFIG=	yes
+
+MAKE_ENV=	CXXFLAGS="${CXXFLAGS}"
 
 DOCS=		*.md
 EXAMPLES=	*
 
-OPTIONS_DEFINE=	DOCS EXAMPLES
-OPTIONS_SUB=	yes
-
 PLIST_SUB=	PORTVERSION=${PORTVERSION} \
 		SHLIB_VER=${PORTVERSION:R}
 
+OPTIONS_DEFINE=	DOCS EXAMPLES
+OPTIONS_SUB=	yes
+
 do-install-DOCS-on:
 	@${MKDIR} ${STAGEDIR}${DOCSDIR}
 	${INSTALL_DATA} ${DOCS:S|^|${WRKSRC}/|} ${STAGEDIR}${DOCSDIR}