diff --git a/Makefile b/Makefile
index 3e2a6e89..b2ab9f35 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,11 @@ pokeblue_obj := $(rom_obj:.o=_blue.o)
 
 ### Build tools
 
-MD5 := md5sum -c
+ifeq (,$(shell which sha1sum))
+SHA1 := shasum
+else
+SHA1 := sha1sum
+endif
 
 RGBDS ?=
 RGBASM  ?= $(RGBDS)rgbasm
@@ -47,9 +51,8 @@ tidy:
 	rm -f $(roms) $(pokered_obj) $(pokeblue_obj) $(roms:.gbc=.map) $(roms:.gbc=.sym) rgbdscheck.o
 	$(MAKE) clean -C tools/
 
-# For contributors to make sure a change didn't affect the original contents of the ROMs.
 compare: $(roms)
-	@$(MD5) roms.md5
+	@$(SHA1) -c roms.sha1
 
 tools:
 	$(MAKE) -C tools/
diff --git a/roms.md5 b/roms.md5
deleted file mode 100644
index c4128cfd..00000000
--- a/roms.md5
+++ /dev/null
@@ -1,2 +0,0 @@
-3d45c1ee9abd5738df46d2bdda8b57dc  pokered.gbc
-50927e843568814f7ed45ec4f944bd8b  pokeblue.gbc
diff --git a/roms.sha1 b/roms.sha1
new file mode 100644
index 00000000..742056ac
--- /dev/null
+++ b/roms.sha1
@@ -0,0 +1,2 @@
+ea9bcae617fdf159b045185467ae58b2e4a48b9a  pokered.gbc
+d7037c83e1ae5b39bde3c30787637ba1d4c48ce2  pokeblue.gbc