diff --git a/Makefile b/Makefile
index 2738966..1b0d84d 100644
--- a/Makefile
+++ b/Makefile
@@ -115,7 +115,9 @@
 KBUILD_OUTPUT := $(shell cd $(KBUILD_OUTPUT) && /bin/pwd)
 $(if $(KBUILD_OUTPUT),, \
      $(error output directory "$(saved-output)" does not exist))
-
+# Check that OUTPUT directory is not the same as where we have kernel src
+$(if $(filter-out $(KBUILD_OUTPUT),$(shell /bin/pwd)),, \
+     $(error Output directory (O=...) specifies kernel src dir))
 PHONY += $(MAKECMDGOALS)
 
 $(filter-out _all,$(MAKECMDGOALS)) _all: