diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 52894f0c..61e67869 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -102,7 +102,7 @@ end
       def build_serializer_class(resource, options)
         "".tap do |klass_name|
           klass_name << "#{options[:namespace]}::" if options[:namespace]
-          klass_name << options[:prefix].to_s.classify       if options[:prefix]
+          klass_name << options[:prefix].to_s.classify if options[:prefix]
           klass_name << "#{resource.class.name}Serializer"
         end
       end