The vgabios build must depend on autoconf.h.
diff --git a/Makefile b/Makefile
index dfcccef..f8f8fc4 100644
--- a/Makefile
+++ b/Makefile
@@ -172,7 +172,7 @@
SRCVGA=src/output.c src/util.c vgasrc/vga.c vgasrc/vgafb.c vgasrc/vgaio.c \
vgasrc/vgatables.c vgasrc/vgafonts.c vgasrc/clext.c
-$(OUT)vgaccode.16.s: ; $(call whole-compile, $(CFLAGS16) -S -Isrc, $(SRCVGA),$@)
+$(OUT)vgaccode.16.s: $(OUT)autoconf.h ; $(call whole-compile, $(CFLAGS16) -S -Isrc, $(SRCVGA),$@)
$(OUT)vgalayout16.o: vgaentry.S $(OUT)vgaccode.16.s $(OUT)asm-offsets.h
@echo " Compiling (16bit) $@"