diff --git a/lib/active_model/serializer/adapter/json_api.rb b/lib/active_model/serializer/adapter/json_api.rb
index 4cb31643..8eafe166 100644
--- a/lib/active_model/serializer/adapter/json_api.rb
+++ b/lib/active_model/serializer/adapter/json_api.rb
@@ -102,9 +102,8 @@ module ActiveModel
         end
 
         def serializable_hash_for_single_resource
-          primary_data = primary_data_for(serializer)
-          relationships = relationships_for(serializer)
-          primary_data[:relationships] = relationships if relationships.any?
+          primary_data = resource_object_for(serializer)
+
           hash = { data: primary_data }
 
           included = included_resources(@include_tree, [primary_data])
@@ -142,26 +141,22 @@ module ActiveModel
         end
 
         def resource_object_for(serializer)
-          cache_check(serializer) do
+          resource_object = cache_check(serializer) do
             resource_object = resource_identifier_for(serializer)
 
             requested_fields = fieldset && fieldset.fields_for(resource_object[:type])
             attributes = attributes_for(serializer, requested_fields)
             resource_object[:attributes] = attributes if attributes.any?
-
-            links = links_for(serializer)
-            resource_object[:links] = links if links.any?
-
             resource_object
           end
-        end
 
-        def primary_data_for(serializer)
-          if serializer.respond_to?(:each)
-            serializer.map { |s| resource_object_for(s) }
-          else
-            resource_object_for(serializer)
-          end
+          relationships = relationships_for(serializer)
+          resource_object[:relationships] = relationships if relationships.any?
+
+          links = links_for(serializer)
+          resource_object[:links] = links if links.any?
+
+          resource_object
         end
 
         def relationship_value_for(serializer, options = {})
@@ -201,9 +196,7 @@ module ActiveModel
           else
             return unless serializer && serializer.object
 
-            resource_object = primary_data_for(serializer)
-            relationships = relationships_for(serializer)
-            resource_object[:relationships] = relationships if relationships.any?
+            resource_object = resource_object_for(serializer)
 
             return if included.include?(resource_object) || primary_data.include?(resource_object)
             included.push(resource_object)