diff --git a/lib/i18n/backend/fallbacks.rb b/lib/i18n/backend/fallbacks.rb
index 7688c13d..1acdbd68 100644
--- a/lib/i18n/backend/fallbacks.rb
+++ b/lib/i18n/backend/fallbacks.rb
@@ -49,7 +49,7 @@ def translate(locale, key, options = EMPTY_HASH)
             catch(:exception) do
               result = super(fallback, key, fallback_options)
               unless result.nil?
-                on_fallback(locale, fallback, key, options) if locale != fallback
+                on_fallback(locale, fallback, key, options) if locale.to_s != fallback.to_s
                 return result
               end
             end
diff --git a/test/backend/fallbacks_test.rb b/test/backend/fallbacks_test.rb
index a3b0dcd0..d2c9ad36 100644
--- a/test/backend/fallbacks_test.rb
+++ b/test/backend/fallbacks_test.rb
@@ -342,4 +342,9 @@ def setup
     assert_equal [:'de-DE', :de, :bar, {}], I18n.backend.fallback_collector[0]
     assert_equal [:'de-DE', :en, :foo, {}], I18n.backend.fallback_collector[1]
   end
+
+  test "on_fallback should not be called when use a String locale" do
+    assert_equal 'Bar in :de', I18n.t("bar", locale: "de")
+    assert I18n.backend.fallback_collector.nil?
+  end
 end