diff --git a/Makefile b/Makefile
index cf1d128..495b32f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 BUILDDIR=.build
-_BIN= cpm22.bin bios.bin
+_BIN= system.bin
 BIN = $(patsubst %,$(BUILDDIR)/%,$(_BIN))
 
 .PHONY: all clean
@@ -9,6 +9,9 @@ all: $(BUILDDIR) $(BIN)
 $(BUILDDIR)/%.bin: src/%.z80 | $(BUILDDIR) 
 	@zasm -w -i $< -o $@
 
+$(BUILDDIR)/system.bin: $(BUILDDIR)/cpm22.bin $(BUILDDIR)/bios.bin | $(BUILDDIR)
+	@python -c "in1 = open('$(BUILDDIR)/cpm22.bin', 'rb').read(); in2 = open('$(BUILDDIR)/bios.bin', 'rb').read(); f = open('$(BUILDDIR)/system.bin', 'wb'); f.write(in1); f.seek(0x1600); f.write(in2)"
+
 $(BUILDDIR)/%.COM: src/%.z80 | $(BUILDDIR)
 	@zasm -w -i $< -o $@