Index: head/devel/mdb/Makefile
===================================================================
--- head/devel/mdb/Makefile
+++ head/devel/mdb/Makefile
@@ -9,7 +9,7 @@
 
 LICENSE=	CDDL
 
-USES=		uidfix
+USES=		compiler uidfix
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	bsdjhb
@@ -29,6 +29,15 @@
 
 .if !exists(${SRC_BASE}/cddl/compat) || !exists(${SRC_BASE}/sys/cddl/compat)
 IGNORE=		requires full source tree with CDDL sources
+.endif
+
+.if ${OSVERSION} < 1300015 && ${COMPILER_TYPE} == "clang" && \
+    ${COMPILER_VERSION} >= 80
+# clang 8 cannot compile due to enum redefinitions in kernel.h
+BUILD_DEPENDS+=	${LOCALBASE}/bin/clang70:devel/llvm70
+CPP=	${LOCALBASE}/bin/clang-cpp70
+CC=	${LOCALBASE}/bin/clang70
+CXX=	${LOCALBASE}/bin/clang++70
 .endif
 
 pre-install: