diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index eaf9312097f7..bb93101e339e 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -44,7 +44,7 @@ LDLIBS = -lrt -lpthread -lm
 # warnings.
 CFLAGS += -U_FORTIFY_SOURCE
 
-KDIR ?= /lib/modules/$(shell uname -r)/build
+KDIR ?= $(if $(O),$(O),$(realpath ../../../..))
 ifneq (,$(wildcard $(KDIR)/Module.symvers))
 ifneq (,$(wildcard $(KDIR)/include/linux/page_frag_cache.h))
 TEST_GEN_MODS_DIR := page_frag
diff --git a/tools/testing/selftests/mm/page_frag/Makefile b/tools/testing/selftests/mm/page_frag/Makefile
index 8c8bb39ffa28..96e5f646e69b 100644
--- a/tools/testing/selftests/mm/page_frag/Makefile
+++ b/tools/testing/selftests/mm/page_frag/Makefile
@@ -1,5 +1,5 @@
 PAGE_FRAG_TEST_DIR := $(realpath $(dir $(abspath $(lastword $(MAKEFILE_LIST)))))
-KDIR ?= /lib/modules/$(shell uname -r)/build
+KDIR ?= $(if $(O),$(O),$(realpath ../../../../..))
 
 ifeq ($(V),1)
 Q =