diff --git a/library/Makefile b/library/Makefile
index 3b91e25..7ea7867 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -186,6 +186,13 @@
 all: shared static
 endif
 
+ifdef TEST_TIMING_ALT_IMPL
+OBJS_CRYPTO += external_timing_for_test.o
+external_timing_for_test.o: ../tests/src/external_timing/external_timing_for_test.c
+	echo "  CC    $<"
+	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) -I../tests/include -o $@ -c $<
+endif
+
 static: libmbedcrypto.a libmbedx509.a libmbedtls.a
 	cd ../tests && echo "This is a seedfile that contains 64 bytes (65 on Windows)......" > seedfile