diff --git a/lib/active_model/serializable/utils.rb b/lib/active_model/serializable/utils.rb
index efabb6c4..3b5f92c3 100644
--- a/lib/active_model/serializable/utils.rb
+++ b/lib/active_model/serializable/utils.rb
@@ -4,13 +4,15 @@ module ActiveModel
       extend self
 
       def _const_get(const)
-        begin
-          method = RUBY_VERSION >= '2.0' ? :const_get : :qualified_const_get
-          Object.send method, const
-        rescue NameError
-          const.safe_constantize
+        Serializer.serializers_cache.fetch_or_store(const) do
+          begin
+            method = RUBY_VERSION >= '2.0' ? :const_get : :qualified_const_get
+            Object.send method, const
+          rescue NameError
+            const.safe_constantize
+          end
         end
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 82693873..b5ff05da 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -4,6 +4,7 @@ require 'active_model/serializer/association'
 require 'active_model/serializer/config'
 
 require 'thread'
+require 'concurrent/map'
 
 module ActiveModel
   class Serializer
@@ -100,6 +101,10 @@ end
         associate(Association::HasMany, *attrs)
       end
 
+      def serializers_cache
+        @serializers_cache ||= Concurrent::Map.new
+      end
+
       private
 
       def strip_attribute(attr)
diff --git a/lib/active_model_serializers.rb b/lib/active_model_serializers.rb
index 7066ebf4..8b50eb55 100644
--- a/lib/active_model_serializers.rb
+++ b/lib/active_model_serializers.rb
@@ -14,6 +14,9 @@ begin
       ActionController::Base.send(:include, ::ActionController::Serialization)
       ActionController::TestCase.send(:include, ::ActionController::SerializationAssertions)
     end
+    ActionDispatch::Reloader.to_prepare do
+      ActiveModel::Serializer.serializers_cache.clear
+    end
   end
 rescue LoadError
   # rails not installed, continuing