diff --git a/Makefile b/Makefile
index 61f1b6c8a..b51652a00 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,8 @@
-MD5 := md5sum -c
+ifeq (,$(shell which sha1sum))
+SHA1 := shasum
+else
+SHA1 := sha1sum
+endif
 
 .SUFFIXES:
 .PHONY: all clean tools compare crystal crystal11
@@ -36,7 +40,7 @@ clean:
 	rm -f $(roms) $(crystal_obj) $(crystal11_obj) $(roms:.gbc=.map) $(roms:.gbc=.sym)
 
 compare: $(roms)
-	@$(MD5) roms.md5
+	@$(SHA1) -c roms.sha1
 
 tools:
 	make -C tools/
diff --git a/README.md b/README.md
index 51e1b4302..a90c147a7 100644
--- a/README.md
+++ b/README.md
@@ -4,8 +4,8 @@ This is a disassembly of Pokémon Crystal.
 
 It builds the following roms:
 
-* Pokemon - Crystal Version (UE) (V1.0) [C][!].gbc `md5: 9f2922b235a5eeb78d65594e82ef5dde`
-* Pokemon - Crystal Version (UE) (V1.1) [C][!].gbc `md5: 301899b8087289a6436b0a241fbbb474`
+* Pokemon - Crystal Version (UE) (V1.0) [C][!].gbc `sha1: f4cd194bdee0d04ca4eac29e09b8e4e9d818c133`
+* Pokemon - Crystal Version (UE) (V1.1) [C][!].gbc `sha1: f2f52230b536214ef7c9924f483392993e226cfb`
 
 To set up the repository, see [**INSTALL.md**](INSTALL.md).
 
diff --git a/roms.md5 b/roms.md5
deleted file mode 100644
index 79ca0bc51..000000000
--- a/roms.md5
+++ /dev/null
@@ -1,2 +0,0 @@
-9f2922b235a5eeb78d65594e82ef5dde  pokecrystal.gbc
-301899b8087289a6436b0a241fbbb474  pokecrystal11.gbc
diff --git a/roms.sha1 b/roms.sha1
new file mode 100644
index 000000000..3cdf981f6
--- /dev/null
+++ b/roms.sha1
@@ -0,0 +1,2 @@
+f4cd194bdee0d04ca4eac29e09b8e4e9d818c133 *pokecrystal.gbc
+f2f52230b536214ef7c9924f483392993e226cfb *pokecrystal11.gbc