diff --git a/math/topcom/Makefile b/math/topcom/Makefile
index ab3cdce726d8..5dcfb4e11d89 100644
--- a/math/topcom/Makefile
+++ b/math/topcom/Makefile
@@ -18,6 +18,9 @@ LIB_DEPENDS=	libcddgmp.so:math/cddlib \
 USES=		autoreconf gmake localbase:ldflags
 GNU_CONFIGURE=	yes
 
+EXTRACT_AFTER_ARGS=	--exclude ${PORTNAME}-${DISTVERSION}/external \
+			--no-same-owner --no-same-permissions
+
 CFLAGS+=	-I${LOCALBASE}/include/cdd/
 LDFLAGS+=	-lgmp -lgmpxx -lcddgmp
 
@@ -32,9 +35,6 @@ SOPLEX_CXXFLAGS=	-I${LOCALBASE}/include/soplex
 SOPLEX_LIB_DEPENDS=	libsoplex.so:math/SoPlex
 SOPLEX_BROKEN=		not compatible with SoPlex-5.0.2 - missing header, reported to the upstream author vie e-mail
 
-post-extract:
-	@${RM} -r ${WRKSRC}/external
-
 post-patch:
 	@${FIND} ${WRKSRC} -name "Makefile*" \
 		| ${XARGS} ${REINPLACE_CMD} ' \