diff --git a/ext/-test-/bignum/depend b/ext/-test-/bignum/depend
new file mode 100644
index 0000000000..2787ca3196
--- /dev/null
+++ b/ext/-test-/bignum/depend
@@ -0,0 +1,3 @@
+$(OBJS): $(HDRS) $(ruby_headers)
+
+export.o: export.c $(top_srcdir)/internal.h