diff --git a/lib/redmine/i18n.rb b/lib/redmine/i18n.rb
index 1e52439fc..b1066539f 100644
--- a/lib/redmine/i18n.rb
+++ b/lib/redmine/i18n.rb
@@ -159,14 +159,14 @@ module Redmine
     # * available_locales are determined by looking at translation file names
     class Backend < ::I18n::Backend::Simple
       module Implementation
-        include ::I18n::Backend::Pluralization
-
         # Get available locales from the translations filenames
         def available_locales
           @available_locales ||= ::I18n.load_path.map {|path| File.basename(path, '.*')}.uniq.sort.map(&:to_sym)
         end
       end
 
+      # Adds custom pluralization rules
+      include ::I18n::Backend::Pluralization
       # Adds fallback to default locale for untranslated strings
       include ::I18n::Backend::Fallbacks
     end
diff --git a/test/unit/lib/redmine/i18n_test.rb b/test/unit/lib/redmine/i18n_test.rb
index 4856c5190..4e15ae56b 100644
--- a/test/unit/lib/redmine/i18n_test.rb
+++ b/test/unit/lib/redmine/i18n_test.rb
@@ -255,4 +255,13 @@ class Redmine::I18nTest < ActiveSupport::TestCase
     set_language_if_valid 'fr'
     assert_equal 'French (Français)', l(:general_lang_name)
   end
+
+  def test_custom_pluralization_rules
+    I18n.backend.store_translations :pt, i18n: {plural: {rule: ->(n) {[0, 1].include?(n) ? :one : :other }}}
+    I18n.backend.store_translations :pt, apples: {one: 'one or none', other: 'more than one'}
+    assert_equal 'one or none', ll(:pt, :apples, count: 0)
+    assert_equal 'more than one', ll(:pt, :apples, count: 2)
+  ensure
+    I18n.reload!
+  end
 end