diff --git a/Makefile.inc1 b/Makefile.inc1
index b870f98e24dc..ed27d74c40ed 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -734,7 +734,7 @@ TMAKE=		\
 # TOOLS_PREFIX set in BMAKE
 XMAKE=		${BMAKE} \
 		TARGET=${TARGET} TARGET_ARCH=${TARGET_ARCH} \
-		MK_CLANG_IS_CC=yes \
+		MK_CLANG_IS_CC=${MK_CLANG_BOOTSTRAP} \
 		MK_GDB=no MK_TESTS=no
 
 # kernel-tools stage