diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index f0a23381..d89bfb2f 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -22,11 +22,25 @@ module ActiveModel
         SETTINGS[:include] = true if options[:include]
       end
 
-      def serializer_for(resource)
-        if resource.respond_to?(:to_ary)
-          ArraySerializer
-        else
-          "#{resource.class.name}Serializer".safe_constantize
+      if RUBY_VERSION >= '2.0'
+        def serializer_for(resource)
+          if resource.respond_to?(:to_ary)
+            ArraySerializer
+          else
+            begin
+              Object.const_get "#{resource.class.name}Serializer"
+            rescue NameError
+              nil
+            end
+          end
+        end
+      else
+        def serializer_for(resource)
+          if resource.respond_to?(:to_ary)
+            ArraySerializer
+          else
+            "#{resource.class.name}Serializer".safe_constantize
+          end
         end
       end