6 files changed, 13 insertions, 2 deletions
diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 2fb7f29d73..7962427032 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Cache `ActiveSupport::TimeWithZone#to_datetime` before freezing.
+
+    *Adam Rice*
+
 *   Deprecate `.halt_callback_chains_on_return_false`.
 
     *Rafael Mendonça França*
diff --git a/activesupport/lib/active_support/duration/iso8601_serializer.rb b/activesupport/lib/active_support/duration/iso8601_serializer.rb
index 51d53e2f8d..e5d458b3ab 100644
--- a/activesupport/lib/active_support/duration/iso8601_serializer.rb
+++ b/activesupport/lib/active_support/duration/iso8601_serializer.rb
@@ -4,7 +4,7 @@ require "active_support/core_ext/hash/transform_values"
 module ActiveSupport
   class Duration
     # Serializes duration to string according to ISO 8601 Duration format.
-    class ISO8601Serializer
+    class ISO8601Serializer # :nodoc:
       def initialize(duration, precision: nil)
         @duration = duration
         @precision = precision
diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
index 889f71c4f3..857cc1a664 100644
--- a/activesupport/lib/active_support/time_with_zone.rb
+++ b/activesupport/lib/active_support/time_with_zone.rb
@@ -427,7 +427,8 @@ module ActiveSupport
     end
 
     def freeze
-      period; utc; time # preload instance variables before freezing
+      # preload instance variables before freezing
+      period; utc; time; to_datetime
       super
     end
 
diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index 5d90fa2509..41cc9888c6 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -1,5 +1,6 @@
 require "date"
 require "abstract_unit"
+require "timeout"
 require "inflector_test_cases"
 require "constantize_test_cases"
 
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index ab5ec98642..1534daacb9 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -507,6 +507,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     assert_nothing_raised do
       @twz.period
       @twz.time
+      @twz.to_datetime
     end
   end
 
diff --git a/activesupport/test/json/encoding_test_cases.rb b/activesupport/test/json/encoding_test_cases.rb
index b2f0cf3048..7e4775cec8 100644
--- a/activesupport/test/json/encoding_test_cases.rb
+++ b/activesupport/test/json/encoding_test_cases.rb
@@ -1,4 +1,8 @@
 require "bigdecimal"
+require "date"
+require "time"
+require "pathname"
+require "uri"
 
 module JSONTest
   class Foo