diff --git a/lib/redmine/field_format.rb b/lib/redmine/field_format.rb
index e3ebc0398..b41b2986c 100644
--- a/lib/redmine/field_format.rb
+++ b/lib/redmine/field_format.rb
@@ -130,6 +130,8 @@ module Redmine
           if value.empty?
             value << ''
           end
+        elsif custom_field.field_format == 'float'
+          value = normalize_float(value)
         else
           value = value.to_s
         end
@@ -540,7 +542,6 @@ module Redmine
       end
 
       def validate_single_value(custom_field, value, customized=nil)
-        value = normalize_float(value)
         errs = super
         errs << ::I18n.t('activerecord.errors.messages.invalid') unless Kernel.Float(value, exception: false)
         errs
diff --git a/lib/redmine/i18n.rb b/lib/redmine/i18n.rb
index 6d893ad22..dc59819a2 100644
--- a/lib/redmine/i18n.rb
+++ b/lib/redmine/i18n.rb
@@ -111,7 +111,7 @@ module Redmine
     #       will clash with the dot separator.
     def normalize_float(value)
       separator = ::I18n.t('number.format.separator')
-      value.gsub(/[#{separator}]/, separator => '.')
+      value.to_s.gsub(/[#{separator}]/, separator => '.')
     end
 
     def day_name(day)
diff --git a/test/unit/lib/redmine/field_format/numeric_format_test.rb b/test/unit/lib/redmine/field_format/numeric_format_test.rb
index 2c9ecdc2e..7e5194d9a 100644
--- a/test/unit/lib/redmine/field_format/numeric_format_test.rb
+++ b/test/unit/lib/redmine/field_format/numeric_format_test.rb
@@ -33,13 +33,21 @@ class Redmine::NumericFieldFormatTest < ActionView::TestCase
     assert_equal '<a href="http://foo/3" class="external">3</a>', field.format.formatted_custom_value(self, custom_value, true)
   end
 
-  def test_float_field_value_should_validate_when_given_with_various_separator
+  def test_float_field_should_normalize_decimal_separator
     field = IssueCustomField.generate!(field_format: 'float')
     issue = Issue.generate!(tracker: Tracker.find(1), status: IssueStatus.find(1), priority: IssuePriority.find(6))
-    to_test = {'en' => '3.33', 'de' => '3,33'}
-    to_test.each do |locale, expected|
-      with_locale locale do
-        assert field.format.validate_single_value(field, expected, issue)
+
+    with_locale 'de' do
+      issue.custom_field_values = { field.id => '3,33' }
+      assert issue.save!
+      assert_equal '3.33', issue.reload.custom_field_values.last.value
+    end
+
+    # Comma decimal separator is not allowed in English locale
+    with_locale 'en' do
+      issue.custom_field_values = { field.id => '3,33' }
+      assert_raise ActiveRecord::RecordInvalid do
+        issue.save!
       end
     end
   end