diff --git a/README.md b/README.md
index 1692404..a124f85 100644
--- a/README.md
+++ b/README.md
@@ -4,8 +4,8 @@ Provide manageable Let's Encrypt Certificate for Rails.
 
 ## Requirement
 
-* Rails 5+
-* Ruby 2.5+
+* Rails 6.1+
+* Ruby 2.7+
 
 ## Installation
 
diff --git a/gemfiles/rails6.gemfile.lock b/gemfiles/rails6.gemfile.lock
index 67ed2b1..30e15ef 100644
--- a/gemfiles/rails6.gemfile.lock
+++ b/gemfiles/rails6.gemfile.lock
@@ -3,14 +3,14 @@ PATH
   specs:
     rails-letsencrypt (0.10.1)
       acme-client (~> 2.0.0)
-      actionmailer (>= 5.0)
-      actionpack (>= 5.0)
-      actionview (>= 5.0)
-      activemodel (>= 5.0)
-      activerecord (>= 5.0)
-      activesupport (>= 5.0)
+      actionmailer (>= 6.1)
+      actionpack (>= 6.1)
+      actionview (>= 6.1)
+      activemodel (>= 6.1)
+      activerecord (>= 6.1)
+      activesupport (>= 6.1)
       net-smtp
-      railties (>= 5.0)
+      railties (>= 6.1)
       redis
 
 GEM
diff --git a/gemfiles/rails7.gemfile.lock b/gemfiles/rails7.gemfile.lock
index 1bc16eb..86ca862 100644
--- a/gemfiles/rails7.gemfile.lock
+++ b/gemfiles/rails7.gemfile.lock
@@ -3,14 +3,14 @@ PATH
   specs:
     rails-letsencrypt (0.10.1)
       acme-client (~> 2.0.0)
-      actionmailer (>= 5.0)
-      actionpack (>= 5.0)
-      actionview (>= 5.0)
-      activemodel (>= 5.0)
-      activerecord (>= 5.0)
-      activesupport (>= 5.0)
+      actionmailer (>= 6.1)
+      actionpack (>= 6.1)
+      actionview (>= 6.1)
+      activemodel (>= 6.1)
+      activerecord (>= 6.1)
+      activesupport (>= 6.1)
       net-smtp
-      railties (>= 5.0)
+      railties (>= 6.1)
       redis
 
 GEM
diff --git a/rails-letsencrypt.gemspec b/rails-letsencrypt.gemspec
index cf841c2..e4896b8 100644
--- a/rails-letsencrypt.gemspec
+++ b/rails-letsencrypt.gemspec
@@ -19,13 +19,13 @@ Gem::Specification.new do |s|
   s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.md"]
   s.require_paths = ["lib"]
 
-  s.add_dependency "railties", ">= 5.0"
-  s.add_dependency "actionmailer", ">= 5.0"
-  s.add_dependency "actionpack", ">= 5.0"
-  s.add_dependency "actionview", ">= 5.0"
-  s.add_dependency "activemodel", ">= 5.0"
-  s.add_dependency "activerecord", ">= 5.0"
-  s.add_dependency "activesupport", ">= 5.0"
+  s.add_dependency "railties", ">= 6.1"
+  s.add_dependency "actionmailer", ">= 6.1"
+  s.add_dependency "actionpack", ">= 6.1"
+  s.add_dependency "actionview", ">= 6.1"
+  s.add_dependency "activemodel", ">= 6.1"
+  s.add_dependency "activerecord", ">= 6.1"
+  s.add_dependency "activesupport", ">= 6.1"
   s.add_dependency "acme-client", "~> 2.0.0"
   s.add_dependency "redis"
   s.add_dependency "net-smtp" if RUBY_VERSION >= '3'