diff --git a/Gemfile b/Gemfile
index 949fe86d2..aeacf54ba 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,6 +1,6 @@
 source 'https://rubygems.org'
 
-ruby '>= 2.5.0', '< 3.1.0'
+ruby '>= 2.5.0', '< 3.2.0'
 gem 'bundler', '>= 1.12.0'
 
 gem 'rails', '6.1.4.1'
@@ -26,6 +26,12 @@ gem 'tzinfo-data', platforms: [:mingw, :x64_mingw, :mswin]
 gem 'rotp'
 gem 'rqrcode'
 
+unless Gem.ruby_version.release < Gem::Version.new('3.1.0')
+  gem 'net-smtp', '~> 0.3.0'
+  gem 'net-imap', '~> 0.2.2'
+  gem 'net-pop', '~> 0.1.1'
+end
+
 # Optional gem for LDAP authentication
 group :ldap do
   gem 'net-ldap', '~> 0.17.0'
@@ -97,7 +103,7 @@ group :test do
   gem "ffi", platforms: [:mingw, :x64_mingw, :mswin]
   # For running system tests
   gem 'puma'
-  gem 'capybara', '~> 3.35.3'
+  gem 'capybara', (Gem.ruby_version < Gem::Version.new('2.6.0') ? '~> 3.35.3' : '~> 3.36.0')
   gem "selenium-webdriver", "~> 3.142.7"
   gem 'webdrivers', '4.6.1', require: false
   # RuboCop
diff --git a/app/models/setting.rb b/app/models/setting.rb
index dfa054028..35512d472 100644
--- a/app/models/setting.rb
+++ b/app/models/setting.rb
@@ -106,7 +106,7 @@ class Setting < ActiveRecord::Base
     v = read_attribute(:value)
     # Unserialize serialized settings
     if available_settings[name]['serialized'] && v.is_a?(String)
-      v = YAML::load(v)
+      v = YAML.respond_to?(:unsafe_load) ? YAML.unsafe_load(v) : YAML.load(v)
       v = force_utf8_strings(v)
     end
     v = v.to_sym if available_settings[name]['format'] == 'symbol' && !v.blank?
diff --git a/doc/INSTALL b/doc/INSTALL
index c0d823b3e..716266dd9 100644
--- a/doc/INSTALL
+++ b/doc/INSTALL
@@ -7,7 +7,7 @@ http://www.redmine.org/
 
 == Requirements
 
-* Ruby 2.5, 2.6, 2.7, 3.0
+* Ruby 2.5, 2.6, 2.7, 3.1
 * Bundler >= 1.12.0
 
 * A database: