diff --git a/actionpack/lib/action_dispatch/journey/router/utils.rb b/actionpack/lib/action_dispatch/journey/router/utils.rb
index f3f540948e..dbc4a88264 100644
--- a/actionpack/lib/action_dispatch/journey/router/utils.rb
+++ b/actionpack/lib/action_dispatch/journey/router/utils.rb
@@ -35,7 +35,7 @@ module ActionDispatch
           US_ASCII = Encoding::US_ASCII
           UTF_8    = Encoding::UTF_8
           EMPTY    = (+"").force_encoding(US_ASCII).freeze
-          DEC2HEX  = (0..255).to_a.map { |i| ENCODE % i }.map { |s| s.force_encoding(US_ASCII) }
+          DEC2HEX  = (0..255).map { |i| (ENCODE % i).force_encoding(US_ASCII) }.freeze
 
           ALPHA = "a-zA-Z"
           DIGIT = "0-9"