diff --git a/lib/jsonapi-resources.rb b/lib/jsonapi-resources.rb
index 04d7908f..e26af1aa 100644
--- a/lib/jsonapi-resources.rb
+++ b/lib/jsonapi-resources.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'jsonapi/resources/railtie'
+require 'jsonapi/utils/polymorphic_types_lookup'
 require 'jsonapi/naive_cache'
 require 'jsonapi/compiled_json'
 require 'jsonapi/relation_retrieval'
diff --git a/lib/jsonapi/relationship.rb b/lib/jsonapi/relationship.rb
index 31a053b2..da706523 100644
--- a/lib/jsonapi/relationship.rb
+++ b/lib/jsonapi/relationship.rb
@@ -87,17 +87,7 @@ def inverse_relationship
     end
 
     def self.polymorphic_types(name)
-      @poly_hash ||= {}.tap do |hash|
-        ObjectSpace.each_object do |klass|
-          next unless Module === klass
-          if ActiveRecord::Base > klass
-            klass.reflect_on_all_associations(:has_many).select { |r| r.options[:as] }.each do |reflection|
-              (hash[reflection.options[:as]] ||= []) << klass.name.underscore
-            end
-          end
-        end
-      end
-      @poly_hash[name.to_sym]
+      ::JSONAPI::Utils::PolymorphicTypesLookup.polymorphic_types(name)
     end
 
     def resource_types
diff --git a/lib/jsonapi/resource_common.rb b/lib/jsonapi/resource_common.rb
index c4731df1..85c81361 100644
--- a/lib/jsonapi/resource_common.rb
+++ b/lib/jsonapi/resource_common.rb
@@ -1020,17 +1020,7 @@ def polymorphic(polymorphic = true)
       end
 
       def _polymorphic_types
-        @poly_hash ||= {}.tap do |hash|
-          ObjectSpace.each_object do |klass|
-            next unless Module === klass
-            if klass < ActiveRecord::Base
-              klass.reflect_on_all_associations(:has_many).select{|r| r.options[:as] }.each do |reflection|
-                (hash[reflection.options[:as]] ||= []) << klass.name.underscore
-              end
-            end
-          end
-        end
-        @poly_hash[_polymorphic_name.to_sym]
+        JSONAPI::Utils.polymorphic_types(_polymorphic_name.to_sym)
       end
 
       def _polymorphic_resource_klasses
diff --git a/lib/jsonapi/utils/polymorphic_types_lookup.rb b/lib/jsonapi/utils/polymorphic_types_lookup.rb
new file mode 100644
index 00000000..2a72673e
--- /dev/null
+++ b/lib/jsonapi/utils/polymorphic_types_lookup.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module JSONAPI
+  module Utils
+    module PolymorphicTypesLookup
+      extend self
+
+      def polymorphic_types(name)
+        polymorphic_types_lookup[name.to_sym]
+      end
+
+      def polymorphic_types_lookup
+        @polymorphic_types_lookup ||= build_polymorphic_types_lookup
+      end
+
+      def build_polymorphic_types_lookup
+        {}.tap do |hash|
+          ObjectSpace.each_object do |klass|
+            next unless Module === klass
+            if ActiveRecord::Base > klass
+              klass.reflect_on_all_associations(:has_many).select { |r| r.options[:as] }.each do |reflection|
+                (hash[reflection.options[:as]] ||= []) << klass.name.underscore
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end