--- number.module	2008-09-03 15:45:05.000000000 +0200
+++ number.module.fixed	2008-10-14 17:15:39.000000000 +0200
@@ -155,6 +155,9 @@
               form_set_error($error_field, t('Illegal value for %name.', array('%name' => t($field['widget']['label']))));
             }
           }
+          else if ($field['required'] && $delta==0){
+            form_set_error($error_field, t('!name field is required.', array('!name' => $field['widget']['label'])));
+          }
         }
       }
       break;