diff --git a/lib/redmine/field_format.rb b/lib/redmine/field_format.rb
index 34591bb..7ccc0ff 100644
--- a/lib/redmine/field_format.rb
+++ b/lib/redmine/field_format.rb
@@ -368,7 +368,7 @@ module Redmine
 
       def validate_single_value(custom_field, value, customized=nil)
         errs = super
-        errs << ::I18n.t('activerecord.errors.messages.not_a_number') unless value =~ /^[+-]?\d+$/
+        errs << ::I18n.t('activerecord.errors.messages.not_a_number') unless value.to_s =~ /^[+-]?\d+$/
         errs
       end
 
diff --git a/test/unit/custom_field_test.rb b/test/unit/custom_field_test.rb
index c20d7f6..e1166c8 100644
--- a/test/unit/custom_field_test.rb
+++ b/test/unit/custom_field_test.rb
@@ -193,6 +193,7 @@ class CustomFieldTest < ActiveSupport::TestCase
     assert f.valid_field_value?('+123')
     assert f.valid_field_value?('-123')
     assert !f.valid_field_value?('6abc')
+    assert f.valid_field_value?(123)
   end
 
   def test_float_field_validation
@@ -205,6 +206,7 @@ class CustomFieldTest < ActiveSupport::TestCase
     assert f.valid_field_value?('-6.250')
     assert f.valid_field_value?('5')
     assert !f.valid_field_value?('6abc')
+    assert f.valid_field_value?(11.2)
   end
 
   def test_multi_field_validation