diff --git a/actionpack/lib/action_dispatch/journey/formatter.rb b/actionpack/lib/action_dispatch/journey/formatter.rb
index 36c041f25474a364d09fc79a960879cdeb5b7190..7d1f5ab7c9d1d5da26fe2579533e77f00ebdb3b3 100644
--- a/actionpack/lib/action_dispatch/journey/formatter.rb
+++ b/actionpack/lib/action_dispatch/journey/formatter.rb
@@ -125,19 +125,10 @@ def non_recursive(cache, options)
           routes
         end
 
-        module RegexCaseComparator
-          DEFAULT_INPUT = /[-_.a-zA-Z0-9]+\/[-_.a-zA-Z0-9]+/
-          DEFAULT_REGEX = /\A#{DEFAULT_INPUT}\Z/
-
-          def self.===(regex)
-            DEFAULT_INPUT == regex
-          end
-        end
-
         # Returns an array populated with missing keys if any are present.
         def missing_keys(route, parts)
           missing_keys = nil
-          tests = route.path.requirements
+          tests = route.path.requirements_for_missing_keys_check
           route.required_parts.each { |key|
             case tests[key]
             when nil
@@ -145,13 +136,8 @@ def missing_keys(route, parts)
                 missing_keys ||= []
                 missing_keys << key
               end
-            when RegexCaseComparator
-              unless RegexCaseComparator::DEFAULT_REGEX.match?(parts[key])
-                missing_keys ||= []
-                missing_keys << key
-              end
             else
-              unless /\A#{tests[key]}\Z/.match?(parts[key])
+              unless tests[key].match?(parts[key])
                 missing_keys ||= []
                 missing_keys << key
               end
diff --git a/actionpack/lib/action_dispatch/journey/path/pattern.rb b/actionpack/lib/action_dispatch/journey/path/pattern.rb
index eaecf0cc37c8c6e1e9a02fffb061ba39a473f852..0d64c6028ba448b23311b1a5bd3e25cd7ab34dbc 100644
--- a/actionpack/lib/action_dispatch/journey/path/pattern.rb
+++ b/actionpack/lib/action_dispatch/journey/path/pattern.rb
@@ -177,6 +177,12 @@ def to_regexp
           @re ||= regexp_visitor.new(@separators, @requirements).accept spec
         end
 
+        def requirements_for_missing_keys_check
+          @requirements_for_missing_keys_check ||= requirements.each_with_object({}) do |(key, regex), hash|
+            hash[key] = /\A#{regex}\Z/
+          end
+        end
+
         private
           def regexp_visitor
             @anchored ? AnchoredRegexp : UnanchoredRegexp
diff --git a/actionpack/test/journey/path/pattern_test.rb b/actionpack/test/journey/path/pattern_test.rb
index 77c19369b03b4c32580dd36e493d93c96604c2e0..2a751bd43729de8328caa4356fcf7744f386b1c4 100644
--- a/actionpack/test/journey/path/pattern_test.rb
+++ b/actionpack/test/journey/path/pattern_test.rb
@@ -289,6 +289,37 @@ def test_named_captures
           named_captures = { "action" => "list", "format" => "rss" }
           assert_equal named_captures, match.named_captures
         end
+
+        def test_requirements_for_missing_keys_check
+          name_regex = /test/
+
+          path = Pattern.build(
+            "/page/:name",
+            { name: name_regex },
+            SEPARATORS,
+            true
+          )
+
+          transformed_regex = path.requirements_for_missing_keys_check[:name]
+          assert_not_nil transformed_regex
+          assert_equal(transformed_regex, /\A#{name_regex}\Z/)
+        end
+
+        def test_requirements_for_missing_keys_check_memoization
+          name_regex = /test/
+
+          path = Pattern.build(
+            "/page/:name",
+            { name: name_regex },
+            SEPARATORS,
+            true
+          )
+
+          first_call = path.requirements_for_missing_keys_check[:name]
+          second_call = path.requirements_for_missing_keys_check[:name]
+
+          assert_equal(first_call.object_id, second_call.object_id)
+        end
       end
     end
   end