diff --git a/lib/dictionary_order_sort/array.rb b/lib/dictionary_order_sort/array.rb
index 86762b1..b36fced 100644
--- a/lib/dictionary_order_sort/array.rb
+++ b/lib/dictionary_order_sort/array.rb
@@ -5,8 +5,9 @@ class Array
   def dict_sort
     sorting_cache = {}
     sort do |a, b|
-      c, d = [a, b].map do |f|
-        sorting_cache[f] ||= f.gsub /\W|[_\s]/, ''
+      c, d = [a, b].map do |el|
+        str = el.to_s
+        sorting_cache[str] ||= str.gsub /\W|[_\s]/, ''
       end
       c <=> d
     end