diff --git a/textproc/heirloom-doctools/Makefile b/textproc/heirloom-doctools/Makefile
index ca7100ad1d5c..5e0f0ce1fae8 100644
--- a/textproc/heirloom-doctools/Makefile
+++ b/textproc/heirloom-doctools/Makefile
@@ -27,6 +27,7 @@ MAKE_ARGS+=	INSTALL="${INSTALL}" \
 		REFDIR=${REFDIR} \
 		ROOT=${STAGEDIR}
 MAKEFILE=	makefile
+CFLAGS+=	-fcommon
 PLIST_SUB=	LIBEXECDIR=libexec/${PORTNAME}
 
 MACDIR?=	${DATADIR}/tmac