diff --git a/test/unit/Filelists.mk b/test/unit/Filelists.mk
index d95923fe..35269412 100644
--- a/test/unit/Filelists.mk
+++ b/test/unit/Filelists.mk
@@ -33,6 +33,7 @@ TESTDIR=$(LWIPDIR)/../test/unit
 TESTFILES=$(TESTDIR)/lwip_unittests.c \
 	$(TESTDIR)/api/test_sockets.c \
 	$(TESTDIR)/arch/sys_arch.c \
+	$(TESTDIR)/core/test_def.c \
 	$(TESTDIR)/core/test_mem.c \
 	$(TESTDIR)/core/test_pbuf.c \
 	$(TESTDIR)/dhcp/test_dhcp.c \