diff --git a/README.md b/README.md
index 5c99f2f..497774b 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,9 @@ A Game Boy ROM disassembler.
 - Uses defines from hardware.inc v2.7 for hardware registers ([source](https://github.com/tobiasvl/hardware.inc))
 - Slow on large ROMs
 
+## Requirements
+
+The assembly files generated by mgbdis are designed to be assembled with [RGBDS](https://rgbds.gbdev.io).
 
 ## Usage
 
diff --git a/mgbdis.py b/mgbdis.py
index 942f112..273af4a 100755
--- a/mgbdis.py
+++ b/mgbdis.py
@@ -1170,7 +1170,7 @@ def write_makefile(self):
         else:
             f.write('\trgblink -n game.sym -m game.map -o $@ $<\n')
         f.write('\trgbfix -v -p 255 $@\n\n')
-        f.write('\tmd5 $@\n\n')
+        f.write('\t@if which md5sum &>/dev/null; then md5sum $@; else md5 $@; fi\n\n')
 
         f.write('clean:\n')
         f.write('\trm -f game.o game.{} game.sym game.map\n'.format(rom_extension))