diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index dcf1da35b..a82163b76 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -684,7 +684,7 @@ module ApplicationHelper
 
   def html_hours(text)
     text.gsub(
-      %r{(\d+)([\.:])(\d+)},
+      %r{(\d+)([\.,:])(\d+)},
       '<span class="hours hours-int">\1</span><span class="hours hours-dec">\2\3</span>'
     ).html_safe
   end
diff --git a/lib/redmine/i18n.rb b/lib/redmine/i18n.rb
index dab486893..6c4d2aad7 100644
--- a/lib/redmine/i18n.rb
+++ b/lib/redmine/i18n.rb
@@ -21,6 +21,8 @@ require 'redmine'
 
 module Redmine
   module I18n
+    include ActionView::Helpers::NumberHelper
+
     def self.included(base)
       base.extend Redmine::I18n
     end
@@ -95,7 +97,7 @@ module Redmine
         m = ((hours - h) * 60).round
         "%d:%02d" % [h, m]
       else
-        "%.2f" % hours.to_f
+        number_with_delimiter(sprintf('%.2f', hours.to_f), delimiter: nil)
       end
     end
 
diff --git a/test/helpers/application_helper_test.rb b/test/helpers/application_helper_test.rb
index 8dccb8b7e..82b1c3278 100644
--- a/test/helpers/application_helper_test.rb
+++ b/test/helpers/application_helper_test.rb
@@ -2171,6 +2171,17 @@ class ApplicationHelperTest < Redmine::HelperTest
     end
   end
 
+  def test_format_hours_should_use_locale_decimal_separator
+    to_test = {'en' => '0.75', 'de' => '0,75'}
+    with_settings :timespan_format => 'decimal' do
+      to_test.each do |locale, expected|
+        with_locale locale do
+          assert_equal expected, format_hours(0.75)
+        end
+      end
+    end
+  end
+
   def test_html_hours
     assert_equal '<span class="hours hours-int">0</span><span class="hours hours-dec">:45</span>',
                  html_hours('0:45')