1 files changed, 4 insertions, 3 deletions
diff --git a/activesupport/lib/active_support/railtie.rb b/activesupport/lib/active_support/railtie.rb
index 6b8fa676a9..605b50d346 100644
--- a/activesupport/lib/active_support/railtie.rb
+++ b/activesupport/lib/active_support/railtie.rb
@@ -70,9 +70,10 @@ module ActiveSupport
     end
 
     initializer "active_support.set_hash_digest_class" do |app|
-      if app.config.active_support.hash_digest_class
-        ActiveSupport::Digest.hash_digest_class =
-          app.config.active_support.hash_digest_class
+      config.after_initialize do
+        if app.config.active_support.use_sha1_digests
+          ActiveSupport::Digest.hash_digest_class = ::Digest::SHA1
+        end
       end
     end
   end