diff --git a/app/controllers/devise_recognisable/sessions_controller.rb b/app/controllers/devise_recognisable/sessions_controller.rb
index 79704b5..e855944 100644
--- a/app/controllers/devise_recognisable/sessions_controller.rb
+++ b/app/controllers/devise_recognisable/sessions_controller.rb
@@ -56,7 +56,8 @@ def check_for_authentication_token
       sign_in_ip: request.location.ip,
       sign_in_at: Time.now,
       user_agent: request.user_agent,
-      accept_header: request.headers["HTTP_ACCEPT"]
+      accept_header: request.headers["HTTP_ACCEPT"],
+      accept_language: request.headers["Accept-Language"]
     )
     redirect_to after_sign_in_path_for(resource)
   end
@@ -69,7 +70,8 @@ def store_recognisable_details
       sign_in_ip: request.location.ip,
       sign_in_at: Time.now,
       user_agent: request.user_agent,
-      accept_header: request.headers["HTTP_ACCEPT"]
+      accept_header: request.headers["HTTP_ACCEPT"],
+      accept_language: request.headers["Accept-Language"]
     )
   end
 end
diff --git a/app/lib/devise_recognisable/guard.rb b/app/lib/devise_recognisable/guard.rb
index c03a48c..98fc32d 100644
--- a/app/lib/devise_recognisable/guard.rb
+++ b/app/lib/devise_recognisable/guard.rb
@@ -8,9 +8,9 @@ class DeviseRecognisable::Guard
   MAX_LEVENSHTEIN_DISTANCE = Rails.env.test? ? 10 : 0
 
   @@required_scores = {
-    relaxed: 2,
-    normal: 3,
-    strict: 4
+    relaxed: 3,
+    normal: 4,
+    strict: 5
   }
 
   def self.with(previous_sessions)
@@ -61,6 +61,9 @@ def calculate_score_for(session)
     # Is the request's Accept header different to the previous sign in?
     score += 1 if session.accept_header == @request.headers["HTTP_ACCEPT"]
 
+    # Is the request's Accept-Language header different to the previous sign in?
+    score += 1 if session.accept_language == @request.headers["Accept-Language"]
+
     return score
   end
 
@@ -165,6 +168,14 @@ def failures
       }
     end
 
+    # Is the request's Accept-Language header different to the previous sign in?
+    unless @closest_match[:session].accept_language == @request.headers["Accept-Language"]
+      failures[:failures][:accept_language] = {
+        request_value: @request.headers["Accept-Language"],
+        session_value: @closest_match[:session].accept_language
+      }
+    end
+
     return failures
   end
 
diff --git a/app/lib/generators/devise_recognisable/install_template.rb.erb b/app/lib/generators/devise_recognisable/install_template.rb.erb
index cbca181..ea1398d 100644
--- a/app/lib/generators/devise_recognisable/install_template.rb.erb
+++ b/app/lib/generators/devise_recognisable/install_template.rb.erb
@@ -6,6 +6,7 @@ class CreateRecognisableSessions < <%= "ActiveRecord::Migration[#{ActiveRecord::
       t.<%= ip_column %> :sign_in_ip
       t.string   :user_agent
       t.string   :accept_header
+      t.string   :accept_language
       t.datetime :sign_in_at
     end
     add_index :recognisable_sessions, [:recognisable_type, :recognisable_id], :name => 'recognisable_index'
diff --git a/spec/dummy-app/db/migrate/20200930175344_create_recognisable_sessions.rb b/spec/dummy-app/db/migrate/20200930175344_create_recognisable_sessions.rb
index da676a0..bce1398 100644
--- a/spec/dummy-app/db/migrate/20200930175344_create_recognisable_sessions.rb
+++ b/spec/dummy-app/db/migrate/20200930175344_create_recognisable_sessions.rb
@@ -6,6 +6,7 @@ def change
       t.string :sign_in_ip
       t.string :user_agent
       t.string :accept_header
+      t.string :accept_language
       t.datetime :sign_in_at
     end
     add_index :recognisable_sessions, [:recognisable_type, :recognisable_id], :name => 'recognisable_index'
diff --git a/spec/dummy-app/db/schema.rb b/spec/dummy-app/db/schema.rb
index 3931582..98655ea 100644
--- a/spec/dummy-app/db/schema.rb
+++ b/spec/dummy-app/db/schema.rb
@@ -17,6 +17,7 @@
     t.string "sign_in_ip"
     t.string "user_agent"
     t.string "accept_header"
+    t.string "accept_language"
     t.datetime "sign_in_at", precision: nil
     t.index ["recognisable_type", "recognisable_id"], name: "recognisable_index"
   end
diff --git a/spec/dummy-app/spec/features/sign_in_spec.rb b/spec/dummy-app/spec/features/sign_in_spec.rb
index d610656..ac9a19e 100644
--- a/spec/dummy-app/spec/features/sign_in_spec.rb
+++ b/spec/dummy-app/spec/features/sign_in_spec.rb
@@ -7,16 +7,19 @@
 
   let!(:user_agent) { 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36' }
   let!(:accept_header) { 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8' }
+  let!(:accept_language) { "en-GB,en-US;q=0.9,en;q=0.8" }
   let!(:recognisable_session_values) {{
     recognisable_id: user.id,
     recognisable_type: 'User',
     user_agent: user_agent,
-    accept_header: accept_header
+    accept_header: accept_header,
+    accept_language: accept_language
   }}
 
   before do
     Capybara.current_session.driver.header('User-Agent', user_agent)
     Capybara.current_session.driver.header('Accept', accept_header)
+    Capybara.current_session.driver.header('Accept-Language', accept_language)
   end
 
   context 'as a user that has no last_sign_in_ip' do
@@ -169,7 +172,7 @@
                 :session_value=>new_ip,
                 :comparison_result=>:complete_mismatch
               }},
-              :score=>2,
+              :score=>3,
               :user_id=>1,
               :user_type=>"User"
               ), "Unrecognised request")
@@ -224,7 +227,7 @@
                 :session_value=>new_ip,
                 :comparison_result=>:complete_mismatch
               }},
-              :score=>2,
+              :score=>3,
               :user_id=>1,
               :user_type=>"User"
               ), "Unrecognised request")
@@ -297,6 +300,7 @@
   context 'from a device with a different Accept header value' do
     let!(:recognisable_session) { FactoryBot.create :recognisable_session, recognisable_session_values }
     let!(:new_accept_header) { 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8' }
+    
 
     before do
       recognisable_session.update!(accept_header: new_accept_header)
@@ -321,14 +325,43 @@
     end
   end
 
+  context 'from a device with a different Accept-Language header value' do
+    let!(:recognisable_session) { FactoryBot.create :recognisable_session, recognisable_session_values }
+    let!(:new_accept_language) { 'en,pl;q=0.9,pl-PL;q=0.8,en-GB-oxendict;q=0.7' }
+
+    before do
+      recognisable_session.update!(accept_header: new_accept_language)
+      visit '/'
+      click_link 'Log in'
+      fill_in 'Email', with: user.email
+      fill_in 'Password', with: user.password
+      click_button 'Log in'
+    end
+
+    it 'does not log the user in' do
+      expect(page).to have_content I18n.t('devise.sessions.send_new_ip_instructions')
+      expect(page).to_not have_content('Home sweet home')
+    end
+
+    context 'visiting the link in the email' do
+      it 'logs the user in' do
+        open_email(user.email, with_subject: I18n.t('devise.mailer.new_ip.subject'))
+        visit_in_email('Log in')
+        expect(page).to have_content('Home sweet home')
+      end
+    end
+  end
+
   context 'with multiple different RecognisableSessions' do
     let!(:different_user_agent) { 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_4) AppleWebKit/605.1.15 (KHTML, like Gecko)' }
     let!(:different_accept_header) { 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8' }
+    let!(:different_accept_language) { 'en,pl;q=0.9,pl-PL;q=0.8,en-GB-oxendict;q=0.7' }
     let!(:different_recognisable_session_values) {{
       recognisable_id: user.id,
       recognisable_type: 'User',
       user_agent: different_user_agent,
-      accept_header: different_accept_header
+      accept_header: different_accept_header,
+      accept_language: different_accept_language
     }}
 
     before do