diff --git a/tools/testing/selftests/sync/Makefile b/tools/testing/selftests/sync/Makefile
index 4981c6b6d050..43db80b71e80 100644
--- a/tools/testing/selftests/sync/Makefile
+++ b/tools/testing/selftests/sync/Makefile
@@ -2,9 +2,11 @@ CFLAGS += -O2 -g -std=gnu89 -pthread -Wall -Wextra
 CFLAGS += -I../../../../usr/include/
 LDFLAGS += -pthread
 
-TEST_PROGS = sync_test
+# lib.mk TEST_CUSTOM_PROGS var is for custome tests that need special
+# build rules. lib.mk will run and install them.
+TEST_CUSTOM_PROGS = sync_test
 
-all: $(TEST_PROGS)
+all: $(TEST_CUSTOM_PROGS)
 
 include ../lib.mk