diff --git a/lib/devise/rails/routes.rb b/lib/devise/rails/routes.rb
index 474766f9d..f43e62fea 100644
--- a/lib/devise/rails/routes.rb
+++ b/lib/devise/rails/routes.rb
@@ -235,7 +235,6 @@ def devise_for(*resources)
       options[:constraints]   = (@scope[:constraints] || {}).merge(options[:constraints] || {})
       options[:defaults]      = (@scope[:defaults] || {}).merge(options[:defaults] || {})
       options[:options]       = @scope[:options] || {}
-      options[:options][:format] = false if options[:format] == false
 
       resources.map!(&:to_sym)
 
@@ -462,7 +461,7 @@ def with_devise_exclusive_scope(new_path, new_as, options) #:nodoc:
         current_scope = @scope.dup
 
         exclusive = { as: new_as, path: new_path, module: nil }
-        exclusive.merge!(options.slice(:constraints, :defaults, :options))
+        exclusive.merge!(options.slice(:constraints, :format, :defaults, :options))
 
         if @scope.respond_to? :new
           @scope = @scope.new exclusive
diff --git a/test/routes_test.rb b/test/routes_test.rb
index f18fb342c..20ba31172 100644
--- a/test/routes_test.rb
+++ b/test/routes_test.rb
@@ -205,7 +205,6 @@ class CustomizedRoutingTest < ActionController::TestCase
 
   test 'map with format false for sessions' do
     expected_params = {controller: 'devise/sessions', action: 'new'}
-    expected_params[:format] = false
 
     assert_recognizes(expected_params, {path: '/htmlonly_admin/sign_in', method: :get})
     assert_raise ExpectedRoutingError do
@@ -215,7 +214,6 @@ class CustomizedRoutingTest < ActionController::TestCase
 
   test 'map with format false for passwords' do
     expected_params = {controller: 'devise/passwords', action: 'create'}
-    expected_params[:format] = false
 
     assert_recognizes(expected_params, {path: '/htmlonly_admin/password', method: :post})
     assert_raise ExpectedRoutingError do
@@ -225,7 +223,6 @@ class CustomizedRoutingTest < ActionController::TestCase
 
   test 'map with format false for registrations' do
     expected_params = {controller: 'devise/registrations', action: 'new'}
-    expected_params[:format] = false
 
     assert_recognizes(expected_params, {path: '/htmlonly_admin/sign_up', method: :get})
     assert_raise ExpectedRoutingError do
@@ -235,7 +232,6 @@ class CustomizedRoutingTest < ActionController::TestCase
 
   test 'map with format false for confirmations' do
     expected_params = {controller: 'devise/confirmations', action: 'show'}
-    expected_params[:format] = false
 
     assert_recognizes(expected_params, {path: '/htmlonly_users/confirmation', method: :get})
     assert_raise ExpectedRoutingError do
@@ -245,7 +241,6 @@ class CustomizedRoutingTest < ActionController::TestCase
 
   test 'map with format false for unlocks' do
     expected_params = {controller: 'devise/unlocks', action: 'show'}
-    expected_params[:format] = false
 
     assert_recognizes(expected_params, {path: '/htmlonly_users/unlock', method: :get})
     assert_raise ExpectedRoutingError do