diff --git a/lib/i18n/backend/base.rb b/lib/i18n/backend/base.rb
index e7b95272..8066bd10 100644
--- a/lib/i18n/backend/base.rb
+++ b/lib/i18n/backend/base.rb
@@ -241,7 +241,7 @@ def load_rb(filename)
         def load_yml(filename)
           begin
             if YAML.respond_to?(:unsafe_load_file) # Psych 4.0 way
-              YAML.unsafe_load_file(filename)
+              YAML.unsafe_load_file(filename, symbolize_names: true, freeze: true)
             else
               YAML.load_file(filename)
             end
diff --git a/test/backend/simple_test.rb b/test/backend/simple_test.rb
index 960e8cc9..701c5c17 100644
--- a/test/backend/simple_test.rb
+++ b/test/backend/simple_test.rb
@@ -72,7 +72,12 @@ def setup
 
   test "simple load_yml: loads data from a YAML file" do
     data = I18n.backend.send(:load_yml, "#{locales_dir}/en.yml")
-    assert_equal({ 'en' => { 'foo' => { 'bar' => 'baz' } } }, data)
+    if ::YAML.respond_to?(:unsafe_load_file)
+      assert_equal({ :en => { :foo => { :bar => 'baz' } } }, data)
+      assert_predicate data.dig(:en, :foo, :bar), :frozen?
+    else
+      assert_equal({ 'en' => { 'foo' => { 'bar' => 'baz' } } }, data)
+    end
   end
 
   test "simple load_json: loads data from a JSON file" do