diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 612f6757015d..0eb5567bb94a 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -78,7 +78,7 @@ override LDFLAGS =
 override MAKEFLAGS =
 endif
 
-# Append kselftest to KBUILD_OUTPUT to avoid cluttering
+# Append kselftest to KBUILD_OUTPUT and O to avoid cluttering
 # KBUILD_OUTPUT with selftest objects and headers installed
 # by selftests Makefile or lib.mk.
 ifdef building_out_of_srctree
@@ -86,7 +86,7 @@ override LDFLAGS =
 endif
 
 ifneq ($(O),)
-	BUILD := $(O)
+	BUILD := $(O)/kselftest
 else
 	ifneq ($(KBUILD_OUTPUT),)
 		BUILD := $(KBUILD_OUTPUT)/kselftest