diff --git a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
index 357b28ac94f3a..092b4ebd2fa04 100644
--- a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
@@ -110,7 +110,7 @@ def belongs_to_options(options)
       rhs_options = {}
 
       if options.key? :class_name
-        rhs_options[:foreign_key] = options[:class_name].foreign_key
+        rhs_options[:foreign_key] = options[:class_name].to_s.foreign_key
         rhs_options[:class_name] = options[:class_name]
       end
 
diff --git a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
index 9a57683ee344f..092e85949ca56 100644
--- a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
@@ -79,6 +79,10 @@ class SubDeveloper < Developer
     :association_foreign_key => "developer_id"
 end
 
+class DeveloperWithSymbolClassName < Developer
+  has_and_belongs_to_many :projects, class_name: :ProjectWithSymbolsForKeys
+end
+
 class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   fixtures :accounts, :companies, :categories, :posts, :categories_posts, :developers, :projects, :developers_projects,
            :parrots, :pirates, :parrots_pirates, :treasures, :price_estimates, :tags, :taggings, :computers
@@ -892,4 +896,10 @@ def test_habtm_with_reflection_using_class_name_and_fixtures
     assert_not_nil File.read(File.expand_path("../../../fixtures/developers.yml", __FILE__)).index("shared_computers")
     assert_equal developers(:david).shared_computers.first, computers(:laptop)
   end
+
+  def test_with_symbol_class_name
+    assert_nothing_raised NoMethodError do
+      DeveloperWithSymbolClassName.new
+    end
+  end
 end