diff --git a/lib/language_list.rb b/lib/language_list.rb
index 4b1386d..ef3897e 100644
--- a/lib/language_list.rb
+++ b/lib/language_list.rb
@@ -63,10 +63,10 @@ def self.find(code)
     warn "Reverting to hash load: #{e.message}"
     yaml_data = YAML.load_file(File.expand_path(File.join(File.dirname(__FILE__),'..', 'data', 'languages.yml')))
     yaml_data.map{|e| LanguageInfo.new(e) }
-  end
-  ISO_639_1 = ALL_LANGUAGES.select(&:iso_639_1?)
-  LIVING_LANGUAGES = ALL_LANGUAGES.select(&:living?)
-  COMMON_LANGUAGES = ALL_LANGUAGES.select(&:common?)
+  end.freeze
+  ISO_639_1 = ALL_LANGUAGES.select(&:iso_639_1?).freeze
+  LIVING_LANGUAGES = ALL_LANGUAGES.select(&:living?).freeze
+  COMMON_LANGUAGES = ALL_LANGUAGES.select(&:common?).freeze
 
   BY_NAME      = {}
   BY_ISO_639_1 = {}
@@ -76,5 +76,7 @@ def self.find(code)
     BY_ISO_639_1[lang.iso_639_1] = lang if lang.iso_639_1
     BY_ISO_639_3[lang.iso_639_3] = lang if lang.iso_639_3
   end
-
+  BY_NAME.freeze
+  BY_ISO_639_1.freeze
+  BY_ISO_639_3.freeze
 end
diff --git a/test/language_list_test.rb b/test/language_list_test.rb
index 96ac9fb..cdac323 100755
--- a/test/language_list_test.rb
+++ b/test/language_list_test.rb
@@ -97,4 +97,34 @@ def test_common_name_when_not_present
     english = LanguageList::LanguageInfo.find('en')
     assert_equal english.name, english.common_name
   end
+
+  def test_cannot_change_constants
+    assert_raises RuntimeError, /frozen Array/i do
+      LanguageList::ALL_LANGUAGES[0] = nil
+    end
+
+    assert_raises RuntimeError, /frozen Array/i do
+      LanguageList::ISO_639_1[0] = nil
+    end
+
+    assert_raises RuntimeError, /frozen Array/i do
+      LanguageList::LIVING_LANGUAGES[0] = nil
+    end
+
+    assert_raises RuntimeError, /frozen Array/i do
+      LanguageList::COMMON_LANGUAGES[0] = nil
+    end
+
+    assert_raises RuntimeError, /frozen Array/i do
+      LanguageList::BY_NAME[0] = nil
+    end
+
+    assert_raises RuntimeError, /frozen Array/i do
+      LanguageList::BY_ISO_639_1[0] = nil
+    end
+
+    assert_raises RuntimeError, /frozen Array/i do
+      LanguageList::BY_ISO_639_3[0] = nil
+    end
+  end
 end