diff --git a/mail/avenger/Makefile b/mail/avenger/Makefile
index 1f22101abd81..64596ee5468a 100644
--- a/mail/avenger/Makefile
+++ b/mail/avenger/Makefile
@@ -26,6 +26,8 @@ CONFIGURE_ENV=	WFLAGS='-Wall'
 CONFIGURE_ARGS=	--enable-ssl=${OPENSSLBASE} \
 		--with-db=${LOCALBASE} \
 		--with-etcdir=${ETCDIR}
+# Fix build with clang11
+CFLAGS+=	-fcommon
 
 OPTIONS_DEFINE=	DOCS SASL