diff --git a/differential/customfield/DifferentialBugzillaBugIDValidator.php b/differential/customfield/DifferentialBugzillaBugIDValidator.php
index 82d6b24..8b1c3d4 100644
--- a/differential/customfield/DifferentialBugzillaBugIDValidator.php
+++ b/differential/customfield/DifferentialBugzillaBugIDValidator.php
@@ -1,111 +1,111 @@
 <?php
 
 class DifferentialBugzillaBugIDValidator extends Phobject {
 
   public static function formatBugID($id) {
     return trim(str_replace('#', '', $id));
   }
 
   public static function validate($bug_id, $account_phid) {
     // This function returns an array of strings representing errors
     // If this function returns an empty array, all data is valid
     $errors = array();
 
     $bug_id = self::formatBugID($bug_id);
 
     // Check for bug ID which may or may not be required at a given time
     if(!strlen($bug_id)) {
       if(PhabricatorEnv::getEnvConfig('bugzilla.require_bugs') === true) {
         $errors[] = pht('Bugzilla Bug ID is required');
       }
       return $errors;
     }
 
     // Isn't a number we can work with
-    if (!ctype_digit($bug_id)) {
-      $errors[] = pht('Bugzilla Bug ID must be a number');
+    if (!ctype_digit($bug_id) || $bug_id === "0") {
+      $errors[] = pht('Bugzilla Bug ID must be a valid bug number');
       return $errors;
     }
 
     // Make a request to BMO to ensure the bug exists and user can see it
 
     // Check to see if the user is an admin; if so, don't validate bug existence
     // because the admin account may not have a BMO account ID associated with it
     $users = id(new PhabricatorPeopleQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withPHIDs(array($account_phid))
       ->withIsAdmin(true)
       ->execute();
     if(count($users)) {
       return $errors;
     }
 
     // Get the transactor's ExternalAccount->accountID using the author's phid
     $users = id(new PhabricatorExternalAccountQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withAccountTypes(array(PhabricatorBMOAuthProvider::ADAPTER_TYPE))
       ->withUserPHIDs(array($account_phid))
       ->execute();
 
     // The only way this should happen is if the user creating/editing the
     // revision isn't tied to a BMO account id (i.e. traditional Phab registration)
     if(!count($users)) {
       $errors[] = pht('This transaction\'s user\'s account ID could not be found.');
       return $errors;
     }
     $user_detail = reset($users);
     $user_bmo_id = $user_detail->getAccountID();
 
     $future_uri = id(new PhutilURI(PhabricatorEnv::getEnvConfig('bugzilla.url')))
       ->setPath('/rest/phabbugz/check_bug/'.$bug_id.'/'.$user_bmo_id);
 
     // http://bugzilla.readthedocs.io/en/latest/api/core/v1/bug.html#get-bug
     // 100 (Invalid Bug Alias) If you specified an alias and there is no bug with that alias.
     // 101 (Invalid Bug ID) The bug_id you specified doesn't exist in the database.
     // 102 (Access Denied) You do not have access to the bug_id you specified.
     $accepted_status_codes = array(100, 101, 102, 200, 404, 500);
 
     $future = id(new HTTPSFuture((string) $future_uri))
       ->setMethod('GET')
       ->addHeader('X-Bugzilla-API-Key', PhabricatorEnv::getEnvConfig('bugzilla.automation_api_key'))
       ->addHeader('Accept', 'application/json')
       ->setExpectStatus($accepted_status_codes)
       ->setTimeout(PhabricatorEnv::getEnvConfig('bugzilla.timeout'));
 
     // Resolve the async HTTPSFuture request and extract JSON body
     try {
       list($status, $body) = $future->resolve();
       $status_code = (int) $status->getStatusCode();
 
       if(in_array($status_code, array(100, 101, 404))) {
         $errors[] = pht('Bugzilla Bug ID: %s does not exist (BMO %s)', $bug_id, $status_code);
       }
       else if($status_code === 102) {
         $errors[] = pht('Bugzilla Bug ID: You do not have permission for this bug.');
       }
       else if($status_code === 500) {
         $errors[] = pht('Bugzilla Bug ID: Bugzilla responded with a 500 error.');
       }
       else if(!in_array($status_code, $accepted_status_codes)) {
         $errors[] = pht('Bugzilla Bug ID:  Bugzilla did not provide an expected response (BMO %s).', $status_code);
       }
       else {
         $json = phutil_json_decode($body);
 
         if($json['result'] != '1') {
           $errors[] = pht('Bugzilla Bug ID:  You do not have permission to view this bug or the bug does not exist.');
         }
 
         // At this point we should be good!  Valid response code and result: 1
       }
     } catch (HTTPFutureResponseStatus $ex) {
       $errors[] = pht(
         'Bugzilla returned an unexpected status code or response body:'.
         'Status code: %s / '.
         'Body: %s',
         $status_code, $body);
     }
 
     return $errors;
   }
 }