diff --git a/lib/tzinfo/country_timezone.rb b/lib/tzinfo/country_timezone.rb
index 23dac7ae..d46bec0d 100644
--- a/lib/tzinfo/country_timezone.rb
+++ b/lib/tzinfo/country_timezone.rb
@@ -79,7 +79,13 @@ def latitude
       # calculated multiple times in concurrently executing threads. It is not 
       # worth the overhead of locking to ensure that @latitude is only 
       # calculated once.
-      @latitude ||= RubyCoreSupport.rational_new!(@latitude_numerator, @latitude_denominator)
+      unless @latitude
+         result = RubyCoreSupport.rational_new!(@latitude_numerator, @latitude_denominator)
+         return result if frozen?
+         @latitude = result
+      end
+
+      @latitude
     end
     
     # The longitude of this timezone in degrees as a Rational.
@@ -88,7 +94,13 @@ def longitude
       # calculated multiple times in concurrently executing threads. It is not 
       # worth the overhead of locking to ensure that @longitude is only 
       # calculated once.
-      @longitude ||= RubyCoreSupport.rational_new!(@longitude_numerator, @longitude_denominator)
+      unless @longitude
+        result = RubyCoreSupport.rational_new!(@longitude_numerator, @longitude_denominator)
+        return result if frozen?
+        @longitude = result
+      end
+
+      @longitude
     end
     
     # Returns true if and only if the given CountryTimezone is equal to the
diff --git a/lib/tzinfo/ruby_country_info.rb b/lib/tzinfo/ruby_country_info.rb
index b23fe8a4..e51915d6 100644
--- a/lib/tzinfo/ruby_country_info.rb
+++ b/lib/tzinfo/ruby_country_info.rb
@@ -22,7 +22,9 @@ def zone_identifiers
       # calculated once.
     
       unless @zone_identifiers
-        @zone_identifiers = zones.collect {|zone| zone.identifier}.freeze
+        result = zones.collect {|zone| zone.identifier}.freeze
+        return result if frozen?
+        @zone_identifiers = result
       end
       
       @zone_identifiers
@@ -40,8 +42,10 @@ def zones
       unless @zones
         zones = Zones.new
         @block.call(zones) if @block
+        result = zones.list.freeze
+        return result if frozen?
         @block = nil
-        @zones = zones.list.freeze
+        @zones = result
       end
       
       @zones
diff --git a/lib/tzinfo/time_or_datetime.rb b/lib/tzinfo/time_or_datetime.rb
index 248d095f..f358005f 100644
--- a/lib/tzinfo/time_or_datetime.rb
+++ b/lib/tzinfo/time_or_datetime.rb
@@ -54,11 +54,14 @@ def to_time
       # calculated once.
     
       unless @time
-        if @timestamp
-          @time = Time.at(@timestamp).utc
+        result = if @timestamp
+          Time.at(@timestamp).utc
         else
-          @time = Time.utc(year, mon, mday, hour, min, sec, usec)
+          Time.utc(year, mon, mday, hour, min, sec, usec)
         end
+
+        return result if frozen?
+        @time = result
       end
       
       @time      
@@ -78,7 +81,9 @@ def to_datetime
         # Avoid using Rational unless necessary.
         u = usec
         s = u == 0 ? sec : Rational(sec * 1000000 + u, 1000000)
-        @datetime = RubyCoreSupport.datetime_new(year, mon, mday, hour, min, s)
+        result = RubyCoreSupport.datetime_new(year, mon, mday, hour, min, s)
+        return result if frozen?
+        @datetime = result
       end
       
       @datetime
@@ -92,7 +97,9 @@ def to_i
       # calculated once.
     
       unless @timestamp
-        @timestamp = to_time.to_i
+        result = to_time.to_i
+        return result if frozen?
+        @timestamp = result
       end
       
       @timestamp
diff --git a/lib/tzinfo/timezone_period.rb b/lib/tzinfo/timezone_period.rb
index eeadfeb3..bc87df24 100644
--- a/lib/tzinfo/timezone_period.rb
+++ b/lib/tzinfo/timezone_period.rb
@@ -71,7 +71,9 @@ def utc_total_offset_rational
       # to ensure that @zone_identifiers is only calculated once.
     
       unless @utc_total_offset_rational
-        @utc_total_offset_rational = OffsetRationals.rational_for_offset(utc_total_offset) 
+        result = OffsetRationals.rational_for_offset(utc_total_offset)
+        return result if frozen?
+        @utc_total_offset_rational = result
       end
       @utc_total_offset_rational
     end
diff --git a/lib/tzinfo/timezone_proxy.rb b/lib/tzinfo/timezone_proxy.rb
index 092bf971..c913011c 100644
--- a/lib/tzinfo/timezone_proxy.rb
+++ b/lib/tzinfo/timezone_proxy.rb
@@ -93,7 +93,13 @@ def real_timezone
         # calculated multiple times in concurrently executing threads. It is not 
         # worth the overhead of locking to ensure that @real_timezone is only 
         # calculated once.
-        @real_timezone ||= Timezone.get(@identifier)
+        unless @real_timezone
+          result = Timezone.get(@identifier)
+          return result if frozen?
+          @real_timezone = result
+        end
+
+        @real_timezone
       end     
   end 
 end
diff --git a/lib/tzinfo/timezone_transition.rb b/lib/tzinfo/timezone_transition.rb
index bb5e3085..b905c627 100644
--- a/lib/tzinfo/timezone_transition.rb
+++ b/lib/tzinfo/timezone_transition.rb
@@ -43,7 +43,12 @@ def local_end_at
       # worth the overhead of locking to ensure that @local_end_at is only
       # calculated once.
     
-      @local_end_at = at.add_with_convert(@previous_offset.utc_total_offset) unless @local_end_at
+      unless @local_end_at
+        result = at.add_with_convert(@previous_offset.utc_total_offset)
+        return result if frozen?
+        @local_end_at = result
+      end
+
       @local_end_at
     end
     
@@ -67,7 +72,12 @@ def local_start_at
       # worth the overhead of locking to ensure that @local_start_at is only
       # calculated once.
     
-      @local_start_at = at.add_with_convert(@offset.utc_total_offset) unless @local_start_at
+      unless @local_start_at
+        result = at.add_with_convert(@offset.utc_total_offset)
+        return result if frozen?
+        @local_start_at = result
+      end
+
       @local_start_at
     end
     
diff --git a/lib/tzinfo/timezone_transition_definition.rb b/lib/tzinfo/timezone_transition_definition.rb
index 26c7da86..016816b8 100644
--- a/lib/tzinfo/timezone_transition_definition.rb
+++ b/lib/tzinfo/timezone_transition_definition.rb
@@ -71,13 +71,16 @@ def at
       # overhead of locking to ensure that @at is only calculated once.
       
       unless @at
-        unless @denominator 
-          @at = TimeOrDateTime.new(@numerator_or_time)
+        result = unless @denominator
+          TimeOrDateTime.new(@numerator_or_time)
         else
           r = RubyCoreSupport.rational_new!(@numerator_or_time, @denominator)
           dt = RubyCoreSupport.datetime_new!(r, 0, Date::ITALY)
-          @at = TimeOrDateTime.new(dt)
+          TimeOrDateTime.new(dt)
         end
+
+        return result if frozen?
+        @at = result
       end
       
       @at
diff --git a/lib/tzinfo/zoneinfo_country_info.rb b/lib/tzinfo/zoneinfo_country_info.rb
index a1230e6e..c99acaa8 100644
--- a/lib/tzinfo/zoneinfo_country_info.rb
+++ b/lib/tzinfo/zoneinfo_country_info.rb
@@ -20,7 +20,9 @@ def zone_identifiers
       # calculated once.
     
       unless @zone_identifiers
-        @zone_identifiers = zones.collect {|zone| zone.identifier}.freeze
+        result = zones.collect {|zone| zone.identifier}.freeze
+        return result if frozen?
+        @zone_identifiers = result
       end
       
       @zone_identifiers
diff --git a/test/tc_country_timezone.rb b/test/tc_country_timezone.rb
index 1bf85bf3..77fd7d14 100644
--- a/test/tc_country_timezone.rb
+++ b/test/tc_country_timezone.rb
@@ -17,6 +17,12 @@ def test_latitude_new!
     ct = CountryTimezone.new!('Europe/London', 2059, 40, -5, 16)
     assert_equal(Rational(2059, 40), ct.latitude)
   end
+
+  def test_latitude_after_freeze_new!
+    ct = CountryTimezone.new!('Europe/London', 2059, 40, -5, 16)
+    ct.freeze
+    assert_equal(Rational(2059, 40), ct.latitude)
+  end
   
   def test_latitude_new
     ct = CountryTimezone.new('Europe/London', Rational(2059, 40), Rational(-5, 16))
@@ -27,6 +33,12 @@ def test_longitude_new!
     ct = CountryTimezone.new!('Europe/London', 2059, 40, -5, 16)
     assert_equal(Rational(-5, 16), ct.longitude)
   end
+
+  def test_longitude_after_freeze_new!
+    ct = CountryTimezone.new!('Europe/London', 2059, 40, -5, 16)
+    ct.freeze
+    assert_equal(Rational(-5, 16), ct.longitude)
+  end
   
   def test_longitude_new
     ct = CountryTimezone.new('Europe/London', Rational(2059, 40), Rational(-5, 16))
diff --git a/test/tc_ruby_country_info.rb b/test/tc_ruby_country_info.rb
index 7893f796..c99f09f6 100644
--- a/test/tc_ruby_country_info.rb
+++ b/test/tc_ruby_country_info.rb
@@ -37,6 +37,19 @@ def test_zone_identifiers
     assert_equal(['ZZ/TimezoneB', 'ZZ/TimezoneA', 'ZZ/TimezoneC', 'ZZ/TimezoneD'], ci.zone_identifiers)
     assert(ci.zone_identifiers.frozen?)
   end
+
+  def test_zone_identifiers_after_freeze
+    ci = RubyCountryInfo.new('ZZ', 'Zzz') do |c|
+      c.timezone('ZZ/TimezoneB', 1, 2, 1, 2, 'Timezone B')
+      c.timezone('ZZ/TimezoneA', 1, 4, 1, 4, 'Timezone A')
+      c.timezone('ZZ/TimezoneC', -10, 3, -20, 7, 'C')
+      c.timezone('ZZ/TimezoneD', -10, 3, -20, 7)
+    end
+
+    ci.freeze
+
+    assert_equal(['ZZ/TimezoneB', 'ZZ/TimezoneA', 'ZZ/TimezoneC', 'ZZ/TimezoneD'], ci.zone_identifiers)
+  end
   
   def test_zones_empty
     ci = RubyCountryInfo.new('ZZ', 'Zzz') {|c| }
@@ -65,6 +78,23 @@ def test_zones
       ci.zones)
     assert(ci.zones.frozen?)
   end
+
+  def test_zones_after_freeze
+    ci = RubyCountryInfo.new('ZZ', 'Zzz') do |c|
+      c.timezone('ZZ/TimezoneB', 1, 2, 1, 2, 'Timezone B')
+      c.timezone('ZZ/TimezoneA', 1, 4, 1, 4, 'Timezone A')
+      c.timezone('ZZ/TimezoneC', -10, 3, -20, 7, 'C')
+      c.timezone('ZZ/TimezoneD', -10, 3, -20, 7)
+    end
+
+    ci.freeze
+
+    assert_equal([CountryTimezone.new!('ZZ/TimezoneB', 1, 2, 1, 2, 'Timezone B'),
+      CountryTimezone.new!('ZZ/TimezoneA', 1, 4, 1, 4, 'Timezone A'),
+      CountryTimezone.new!('ZZ/TimezoneC', -10, 3, -20, 7, 'C'),
+      CountryTimezone.new!('ZZ/TimezoneD', -10, 3, -20, 7)],
+      ci.zones)
+  end
   
   def test_deferred_evaluate
     block_called = false
diff --git a/test/tc_time_or_datetime.rb b/test/tc_time_or_datetime.rb
index 05f574dd..9f38bfbe 100644
--- a/test/tc_time_or_datetime.rb
+++ b/test/tc_time_or_datetime.rb
@@ -128,6 +128,11 @@ def test_to_time_trunc_to_usec
     assert_equal(Time.utc(2006, 3, 24, 15, 32, 3, 721123),
       TimeOrDateTime.new(DateTime.new(2006, 3, 24, 15, 32, 3 + Rational(7211239, 10000000))).to_time)
   end
+
+  def test_to_time_after_freeze
+    assert_equal(Time.utc(2006, 3, 24, 15, 32, 3), TimeOrDateTime.new(DateTime.new(2006, 3, 24, 15, 32, 3)).freeze.to_time)
+    assert_equal(Time.utc(2006, 3, 24, 15, 32, 3), TimeOrDateTime.new(1143214323).freeze.to_time)
+  end
   
   def test_to_datetime
     assert_equal(DateTime.new(2006, 3, 24, 15, 32, 3),
@@ -157,6 +162,11 @@ def test_to_datetime_trunc_to_usec
     assert_equal(DateTime.new(2006, 3, 24, 15, 32, 3 + Rational(721123, 1000000)),
       TimeOrDateTime.new(Time.utc(2006, 3, 24, 15, 32, 3, 721123 + Rational(9, 10))).to_datetime)
   end
+
+  def test_to_datetime_after_freeze
+    assert_equal(DateTime.new(2006, 3, 24, 15, 32, 3), TimeOrDateTime.new(Time.utc(2006, 3, 24, 15, 32, 3)).freeze.to_datetime)
+    assert_equal(DateTime.new(2006, 3, 24, 15, 32, 3), TimeOrDateTime.new(1143214323).freeze.to_datetime)
+  end
   
   def test_to_i
     assert_equal(1143214323,
@@ -172,6 +182,11 @@ def test_to_i
     assert_equal(1143214323,
       TimeOrDateTime.new('1143214323').to_i)
   end
+
+  def test_to_i_after_freeze
+    assert_equal(1143214323, TimeOrDateTime.new(Time.utc(2006, 3, 24, 15, 32, 3)).freeze.to_i)
+    assert_equal(1143214323, TimeOrDateTime.new(DateTime.new(2006, 3, 24, 15, 32, 3)).freeze.to_i)
+  end
   
   def test_to_orig
     assert_equal(Time.utc(2006, 3, 24, 15, 32, 3),
diff --git a/test/tc_timezone_period.rb b/test/tc_timezone_period.rb
index be7ef3fa..bcfb8d57 100644
--- a/test/tc_timezone_period.rb
+++ b/test/tc_timezone_period.rb
@@ -149,6 +149,13 @@ def test_initialize_offset
     assert_nil(p.local_end)
     assert_nil(p.local_end_time)
   end
+
+  def test_utc_total_offset_rational_after_freeze
+    o = TimezoneOffset.new(3600, 0, :TEST)
+    p = TimezonePeriod.new(nil, nil, o)
+    p.freeze
+    assert_equal(Rational(1, 24), p.utc_total_offset_rational)
+  end
   
   def test_dst    
     p1 = TimezonePeriod.new(nil, nil, TimezoneOffset.new(-14400, 3600, :TEST))
diff --git a/test/tc_timezone_proxy.rb b/test/tc_timezone_proxy.rb
index 55718aa6..22ba3d4c 100644
--- a/test/tc_timezone_proxy.rb
+++ b/test/tc_timezone_proxy.rb
@@ -88,6 +88,15 @@ def test_canonical_linked
       assert_same(Timezone.get('UTC'), proxy.canonical_zone)
     end
   end
+
+  def test_after_freeze
+    proxy = TimezoneProxy.new('Europe/London')
+    real = Timezone.get('Europe/London')
+    t = Time.utc(2017, 6, 1)
+    proxy.freeze
+    assert_equal('Europe/London', proxy.identifier)
+    assert_equal(real.utc_to_local(t), proxy.utc_to_local(t))
+  end
   
   def test_equals
     assert_equal(true, TimezoneProxy.new('Europe/London') == TimezoneProxy.new('Europe/London'))
diff --git a/test/tc_timezone_transition.rb b/test/tc_timezone_transition.rb
index 8941ec97..3dba5182 100644
--- a/test/tc_timezone_transition.rb
+++ b/test/tc_timezone_transition.rb
@@ -68,6 +68,13 @@ def test_local_end_at
     assert(TimeOrDateTime.new(DateTime.new(2006, 5, 30, 1, 31, 20)).eql?(t2.local_end_at))
     assert(TimeOrDateTime.new(Time.utc(2006, 5, 30, 1, 31, 20)).eql?(t3.local_end_at))
   end
+
+  def test_local_end_at_after_freeze
+    t = TestTimezoneTransition.new(TimezoneOffset.new(3600, 3600, :TDT),
+      TimezoneOffset.new(3600, 0, :TST), 1148949080)
+    t.freeze
+    assert(TimeOrDateTime.new(1148952680).eql?(t.local_end_at))
+  end
   
   def test_local_end
     t1 = TestTimezoneTransition.new(TimezoneOffset.new(3600, 3600, :TDT),
@@ -107,6 +114,13 @@ def test_local_start_at
     assert(TimeOrDateTime.new(DateTime.new(2006, 5, 30, 2, 31, 20)).eql?(t2.local_start_at))
     assert(TimeOrDateTime.new(Time.utc(2006, 5, 30, 2, 31, 20)).eql?(t3.local_start_at))
   end
+
+  def test_local_start_at_after_freeze
+    t = TestTimezoneTransition.new(TimezoneOffset.new(3600, 3600, :TDT),
+      TimezoneOffset.new(3600, 0, :TST), 1148949080)
+    t.freeze
+    assert(TimeOrDateTime.new(1148956280).eql?(t.local_start_at))
+  end
   
   def test_local_start
     t1 = TestTimezoneTransition.new(TimezoneOffset.new(3600, 3600, :TDT),
diff --git a/test/tc_timezone_transition_definition.rb b/test/tc_timezone_transition_definition.rb
index a542c129..b66233b2 100644
--- a/test/tc_timezone_transition_definition.rb
+++ b/test/tc_timezone_transition_definition.rb
@@ -70,6 +70,17 @@ def test_at_after_32bit
       assert(TimeOrDateTime.new(DateTime.new(2038, 1, 19, 3, 14, 8)).eql?(t.at))
     end
   end
+
+  def test_at_after_freeze
+    t1 = TimezoneTransitionDefinition.new(TimezoneOffset.new(3600, 3600, :TDT),
+      TimezoneOffset.new(3600, 0, :TST), 1148949080)
+    t2 = TimezoneTransitionDefinition.new(TimezoneOffset.new(3600, 3600, :TDT),
+      TimezoneOffset.new(3600, 0, :TST), 5300392727, 2160)
+    t1.freeze
+    t2.freeze
+    assert(TimeOrDateTime.new(1148949080).eql?(t1.at))
+    assert(TimeOrDateTime.new(DateTime.new(2006, 5, 30, 0, 31, 20)).eql?(t2.at))
+  end
   
   def test_eql_timestamp
     t1 = TimezoneTransitionDefinition.new(TimezoneOffset.new(3600, 3600, :TDT),
diff --git a/test/tc_zoneinfo_country_info.rb b/test/tc_zoneinfo_country_info.rb
index 67a06311..f54e9b16 100644
--- a/test/tc_zoneinfo_country_info.rb
+++ b/test/tc_zoneinfo_country_info.rb
@@ -35,6 +35,20 @@ def test_zone_identifiers
     assert(!ci.zones.equal?(zones))
     assert(!zones.frozen?)
   end
+
+  def test_zone_identifiers_after_freeze
+    zones = [
+      CountryTimezone.new('ZZ/TimezoneB', Rational(1, 2), Rational(1, 2), 'Timezone B'),
+      CountryTimezone.new('ZZ/TimezoneA', Rational(1, 4), Rational(1, 4), 'Timezone A'),
+      CountryTimezone.new('ZZ/TimezoneC', Rational(-10, 3), Rational(-20, 7), 'C'),
+      CountryTimezone.new('ZZ/TimezoneD', Rational(-10, 3), Rational(-20, 7))
+    ]
+
+    ci = ZoneinfoCountryInfo.new('ZZ', 'Zzz', zones)
+    ci.freeze
+
+    assert_equal(['ZZ/TimezoneB', 'ZZ/TimezoneA', 'ZZ/TimezoneC', 'ZZ/TimezoneD'], ci.zone_identifiers)
+  end
   
   def test_zones_empty
     ci = ZoneinfoCountryInfo.new('ZZ', 'Zzz', [])