diff --git a/lib/generators/simple_form/templates/config/initializers/simple_form.rb b/lib/generators/simple_form/templates/config/initializers/simple_form.rb
index d26878480..7e9a7a689 100644
--- a/lib/generators/simple_form/templates/config/initializers/simple_form.rb
+++ b/lib/generators/simple_form/templates/config/initializers/simple_form.rb
@@ -173,4 +173,7 @@
   # Defines validation classes to the input_field. By default it's nil.
   # config.input_field_valid_class = 'is-valid'
   # config.input_field_error_class = 'is-invalid'
+
+  # Defines the default form builder when more customization is needed.
+  # config.default_builder = 'SimpleForm::OtherCSSFramework::FormBuilder'
 end
diff --git a/lib/simple_form.rb b/lib/simple_form.rb
index e813398a3..08a8920b0 100644
--- a/lib/simple_form.rb
+++ b/lib/simple_form.rb
@@ -213,6 +213,9 @@ def self.configured? #:nodoc:
   mattr_accessor :input_field_valid_class
   @@input_field_valid_class = nil
 
+  mattr_accessor :default_builder
+  @@default_builder = 'SimpleForm::FormBuilder'
+
   # Retrieves a given wrapper
   def self.wrapper(name)
     @@wrappers[name.to_s] or raise WrapperNotFound, "Couldn't find wrapper with name #{name}"
diff --git a/lib/simple_form/action_view_extensions/builder.rb b/lib/simple_form/action_view_extensions/builder.rb
index 7af4ecc08..2c453cbe4 100644
--- a/lib/simple_form/action_view_extensions/builder.rb
+++ b/lib/simple_form/action_view_extensions/builder.rb
@@ -23,7 +23,7 @@ def simple_fields_for(*args, &block)
         if self.class < ActionView::Helpers::FormBuilder
           options[:builder] ||= self.class
         else
-          options[:builder] ||= SimpleForm::FormBuilder
+          options[:builder] ||= SimpleForm.default_builder.constantize
         end
         fields_for(*args, options, &block)
       end
diff --git a/lib/simple_form/action_view_extensions/form_helper.rb b/lib/simple_form/action_view_extensions/form_helper.rb
index 6981aa983..8b404fc64 100644
--- a/lib/simple_form/action_view_extensions/form_helper.rb
+++ b/lib/simple_form/action_view_extensions/form_helper.rb
@@ -12,7 +12,7 @@ module ActionViewExtensions
     module FormHelper
 
       def simple_form_for(record, options = {}, &block)
-        options[:builder] ||= SimpleForm::FormBuilder
+        options[:builder] ||= SimpleForm.default_builder.constantize
         options[:html] ||= {}
         unless options[:html].key?(:novalidate)
           options[:html][:novalidate] = !SimpleForm.browser_validations
@@ -30,7 +30,7 @@ def simple_form_for(record, options = {}, &block)
 
       def simple_fields_for(record_name, record_object = nil, options = {}, &block)
         options, record_object = record_object, nil if record_object.is_a?(Hash) && record_object.extractable_options?
-        options[:builder] ||= SimpleForm::FormBuilder
+        options[:builder] ||= SimpleForm.default_builder.constantize
 
         with_simple_form_field_error_proc do
           fields_for(record_name, record_object, options, &block)