diff --git a/lib/i18n/backend/cache.rb b/lib/i18n/backend/cache.rb
index 41b58fc2..40c18d65 100644
--- a/lib/i18n/backend/cache.rb
+++ b/lib/i18n/backend/cache.rb
@@ -17,11 +17,11 @@
 #
 # The cache_key implementation by default assumes you pass values that return
 # a valid key from #hash (see
-# http://www.ruby-doc.org/core/classes/Object.html#M000337). However, you can
+# https://www.ruby-doc.org/core/classes/Object.html#M000337). However, you can
 # configure your own digest method via which responds to #hexdigest (see
-# http://ruby-doc.org/stdlib/libdoc/digest/rdoc/index.html):
+# https://ruby-doc.org/stdlib/libdoc/openssl/rdoc/OpenSSL/Digest.html):
 #
-#   I18n.cache_key_digest = Digest::MD5.new
+#   I18n.cache_key_digest = OpenSSL::Digest::SHA256.new
 #
 # If you use a lambda as a default value in your translation like this:
 #
diff --git a/lib/i18n/backend/cache_file.rb b/lib/i18n/backend/cache_file.rb
index 4dafb3e6..0c5e1922 100644
--- a/lib/i18n/backend/cache_file.rb
+++ b/lib/i18n/backend/cache_file.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'digest/sha2'
+require 'openssl'
 
 module I18n
   module Backend
@@ -19,7 +19,7 @@ def load_file(filename)
         key = I18n::Backend::Flatten.escape_default_separator(normalized_path(filename))
         old_mtime, old_digest = initialized && lookup(:i18n, key, :load_file)
         return if (mtime = File.mtime(filename).to_i) == old_mtime ||
-                  (digest = Digest::SHA2.file(filename).hexdigest) == old_digest
+                  (digest = OpenSSL::Digest::SHA256.file(filename).hexdigest) == old_digest
         super
         store_translations(:i18n, load_file: { key => [mtime, digest] })
       end
diff --git a/test/backend/cache_test.rb b/test/backend/cache_test.rb
index a14a0a4c..bd2efbce 100644
--- a/test/backend/cache_test.rb
+++ b/test/backend/cache_test.rb
@@ -1,5 +1,5 @@
 require 'test_helper'
-require 'digest/md5'
+require 'openssl'
 
 begin
   require 'active_support'
@@ -74,11 +74,11 @@ def teardown
   end
 
   test "cache_key uses configured digest method" do
-    md5 = Digest::MD5.new
+    digest = OpenSSL::Digest::SHA256.new
     options = { :bar => 1 }
     options_hash = options.inspect
-    with_cache_key_digest(md5) do
-      assert_equal "i18n//en/#{md5.hexdigest(:foo.to_s)}/#{md5.hexdigest(options_hash)}", I18n.backend.send(:cache_key, :en, :foo, options)
+    with_cache_key_digest(digest) do
+      assert_equal "i18n//en/#{digest.hexdigest(:foo.to_s)}/#{digest.hexdigest(options_hash)}", I18n.backend.send(:cache_key, :en, :foo, options)
     end
   end