diff --git a/lib/active_model/serializer/adapter.rb b/lib/active_model/serializer/adapter.rb
index 852fa53e..7c061434 100644
--- a/lib/active_model/serializer/adapter.rb
+++ b/lib/active_model/serializer/adapter.rb
@@ -33,7 +33,8 @@ module ActiveModel
       end
 
       def self.adapter_class(adapter)
-        "ActiveModel::Serializer::Adapter::#{adapter.to_s.classify}".safe_constantize
+        adapter_name = adapter.to_s.classify.sub("API", "Api")
+        "ActiveModel::Serializer::Adapter::#{adapter_name}".safe_constantize
       end
 
       def fragment_cache(*args)
@@ -42,7 +43,7 @@ module ActiveModel
 
       private
 
-     def cache_check(serializer)
+      def cache_check(serializer)
         @cached_serializer = serializer
         @klass             = @cached_serializer.class
         if is_cached?
diff --git a/test/adapter_test.rb b/test/adapter_test.rb
index 7268c386..3349d8a7 100644
--- a/test/adapter_test.rb
+++ b/test/adapter_test.rb
@@ -38,6 +38,15 @@ module ActiveModel
         adapter = ActiveModel::Serializer::Adapter.create(@serializer, { adapter: :json_api})
         assert_equal ActiveModel::Serializer::Adapter::JsonApi, adapter.class
       end
+
+      def test_inflected_adapter_class_for_known_adapter
+        ActiveSupport::Inflector.inflections(:en){|inflect| inflect.acronym 'API' }
+        klass = ActiveModel::Serializer::Adapter.adapter_class(:json_api)
+
+        ActiveSupport::Inflector.inflections.acronyms.clear
+
+        assert_equal ActiveModel::Serializer::Adapter::JsonApi, klass
+      end
     end
   end
 end