diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
index a5d40653a921..9700281bee4c 100644
--- a/tools/testing/selftests/lib.mk
+++ b/tools/testing/selftests/lib.mk
@@ -26,6 +26,7 @@ include $(top_srcdir)/scripts/subarch.include
 ARCH		?= $(SUBARCH)
 
 .PHONY: khdr
+.NOTPARALLEL:
 khdr:
 	make ARCH=$(ARCH) -C $(top_srcdir) headers_install