diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 3a9b46c7d71..49ef29df009 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -411,6 +411,20 @@ class UnicodeTest(
                 return u'\u1234'
         self.assertEqual('%s' % Wrapper(), u'\u1234')
 
+    def test_format_float(self):
+        try:
+            import locale
+            orig_locale = locale.setlocale(locale.LC_ALL)
+            locale.setlocale(locale.LC_ALL, 'de_DE')
+        except (ImportError, locale.Error):
+            return # skip if we can't set locale
+
+        try:
+            # should not format with a comma, but always with C locale
+            self.assertEqual(u'1.0', u'%.1f' % 1.0)
+        finally:
+            locale.setlocale(locale.LC_ALL, orig_locale)
+
     def test_constructor(self):
         # unicode(obj) tests (this maps to PyObject_Unicode() at C level)