diff --git a/Makefile b/Makefile
index 554eb8a..ce3df65 100644
--- a/Makefile
+++ b/Makefile
@@ -247,6 +247,9 @@ $(GUEST_INIT_S2): guest/init_stage2.c
 
 $(DEPS):
 
+util/rbtree.d: ../../lib/rbtree.c
+	$(Q) $(CC) -M -MT util/rbtree.o $(CFLAGS) $< -o $@
+
 %.d: %.c
 	$(Q) $(CC) -M -MT $(patsubst %.d,%.o,$@) $(CFLAGS) $< -o $@