diff --git a/lib/redmine/field_format.rb b/lib/redmine/field_format.rb
index fade7c257..497147388 100644
--- a/lib/redmine/field_format.rb
+++ b/lib/redmine/field_format.rb
@@ -486,7 +486,7 @@ module Redmine
 
       def validate_single_value(custom_field, value, customized=nil)
         errs = super
-        errs << ::I18n.t('activerecord.errors.messages.not_a_number') unless value.to_s =~ /^[+-]?\d+$/
+        errs << ::I18n.t('activerecord.errors.messages.not_a_number') unless value.to_s.strip =~ /^[+-]?\d+$/
         errs
       end
 
diff --git a/test/unit/custom_field_test.rb b/test/unit/custom_field_test.rb
index 3eae54efa..b49501ed0 100644
--- a/test/unit/custom_field_test.rb
+++ b/test/unit/custom_field_test.rb
@@ -206,6 +206,7 @@ class CustomFieldTest < ActiveSupport::TestCase
     assert f.valid_field_value?('')
     assert !f.valid_field_value?(' ')
     assert f.valid_field_value?('123')
+    assert f.valid_field_value?(' 123 ')
     assert f.valid_field_value?('+123')
     assert f.valid_field_value?('-123')
     assert !f.valid_field_value?('6abc')
@@ -219,6 +220,7 @@ class CustomFieldTest < ActiveSupport::TestCase
     assert f.valid_field_value?('')
     assert !f.valid_field_value?(' ')
     assert f.valid_field_value?('11.2')
+    assert f.valid_field_value?(' 11.2 ')
     assert f.valid_field_value?('-6.250')
     assert f.valid_field_value?('5')
     assert !f.valid_field_value?('6abc')