diff --git a/arcanist/workflow/ArcanistLandBotWorkflow.php b/arcanist/workflow/ArcanistLandBotWorkflow.php
index 548bbd3ff..e8703ba09 100644
--- a/arcanist/workflow/ArcanistLandBotWorkflow.php
+++ b/arcanist/workflow/ArcanistLandBotWorkflow.php
@@ -1,204 +1,218 @@
 <?php
 
 /**
  * Lands a revision by sending it to a remote land bot service.
  */
 final class ArcanistLandBotWorkflow extends ArcanistWorkflow {
 
   public function getWorkflowName() {
     return 'land-via-bot';
   }
 
   public function getCommandSynopses() {
     return phutil_console_format(<<<EOTEXT
       **land-via-bot** [__options__] [__ref__]
 EOTEXT
       );
   }
 
   public function getCommandHelp() {
     return phutil_console_format(<<<EOTEXT
           Publish an accepted revision after review. This command is the last
           step in the standard Differential code review workflow.
 
           This command queues a revision to be landed by a remote land bot,
           changes for which are sitting in __ref__, which is usually the name
           of a local branch.  Without __ref__, the current working copy state
           will be used.
 
           Prior to landing the revision, the land bot may run smoke tests and
           other checks to ensure master is always in a stable state. The land
           bot may also make automated adjustments to your patch as necessary.
 
           With **--hold** or **--preview**, execution will be similar to
           passing the same options to 'arc land'.
 EOTEXT
       );
   }
 
   public function requiresWorkingCopy() {
     return true;
   }
 
   public function requiresConduit() {
     return true;
   }
 
   public function requiresAuthentication() {
     return true;
   }
 
   public function requiresRepositoryAPI() {
     return true;
   }
 
   public function getArguments() {
     return array(
       'hold' => array(
         'help' => pht(
           'Prepare the change to be pushed to the land queue, but do not '.
           'actually push it.'),
       ),
       'preview' => array(
         'help' => pht(
           'Prints the commits that would be landed. Does not actually modify '.
           'or land the commits.'),
       ),
       'revision' => array(
         'param' => 'id',
         'help' => pht(
           'Land a specific revision, rather than inferring the revision '.
           'based on branch content.'),
       ),
       '*' => 'branch',
     );
   }
 
   public function run() {
     // Make sure gpg is installed
     try {
       execx('command -v gpg');
     } catch (Exception $e) {
       throw new ArcanistUsageException(pht(
         'gpg not found. Try installing it first.'));
     }
 
     // Determine the branch you are currently on so we can return to it later
     $repositoryApi = $this->getRepositoryAPI();
     $oldBranch = $repositoryApi->getBranchName();
     if (!strlen($oldBranch)) {
       $oldBranch = $repositoryApi->getWorkingCopyRevision();
     }
 
     // Run the default land workflow to take advantage of various sanity checks
     // and fetch the revision ID if it's not set via --revision.
     $landArgs = array();
     if ($this->getArgument('preview')) {
       array_push($landArgs, '--preview');
     } else {
       // Always hold the revision since we are not using 'arc land' to actually
       // land the change.
       array_push($landArgs, '--hold');
     }
 
     // Checkout the specified branch/commit which will determine the revision
     // to land. Your old branch will be restored at the end.
     $branch = $this->getArgument('branch');
     if (!empty($branch)) {
-      $repositoryApi->execxLocal('checkout %s', $branch[0]);
+      $branch = $branch[0];
+      $repositoryApi->execxLocal('checkout %s', $branch);
     }
 
     $revision = $this->getArgument('revision');
     if (empty($revision)) {
       // By default, queue the latest revision on the current branch
       $revisions = $repositoryApi->loadWorkingCopyDifferentialRevisions(
         $this->getConduit(), array());
+
+      if (empty($revisions)) {
+        $location = 'current branch';
+        if (!empty($branch)) {
+          // Restore the branch you were on previously
+          $repositoryApi->execxLocal('checkout %s', $oldBranch);
+
+          $location = "'$branch'";
+        }
+        throw new ArcanistUsageException(pht(
+          "Error: Could not find a valid revision at %s", $location));
+      }
+
       $revision = 'D' . end($revisions)['id'];
     }
     array_push($landArgs, '--revision');
     array_push($landArgs, $revision);
 
     if ($this->getArgument('preview')) {
       // Restore the branch you were on previously
       $repositoryApi->execxLocal('checkout %s', $oldBranch);
 
       echo phutil_console_format(pht(
         'Found revision %s', $revision) . "\n");
       return 0;
     }
 
     $landWorkflow = $this->buildChildWorkflow('land', $landArgs);
     $landWorkflow->run();
 
     // Restore the branch you were on previously
     $repositoryApi->execxLocal('checkout %s', $oldBranch);
 
     if ($this->getArgument('hold')) {
       echo phutil_console_format(pht(
         'Revision %s has not been queued with the land bot', $revision) . "\n");
       return 0;
     }
 
     // Encrypt your Conduit token to securely pass it to the land bot
     $workingCopy = $repositoryApi->getWorkingCopyIdentity();
     $pubkeyFile = $workingCopy->getProjectPath(
       './contrib/source-control-tools/land-patch.pub');
     $token = $this->getConduit()->getConduitToken();
     list($encryptedToken) = execx(
       'echo %s | gpg --armor -o- --encrypt --recipient-file %s',
       $token, $pubkeyFile);
 
     // Clear and delete the unencrypted $token
     $tokenLen = strlen($token);
     for ($i = 0; $i < $tokenLen; $i++) {
       $token[$i] = "\0";
     }
     unset($token);
 
     // Get the configured committer name and email similar to how
     // ArcanistGitAPI::getAuthor() does. Arcanist provides no API for this.
     list($gitIdent) = $repositoryApi->execxLocal('var GIT_COMMITTER_IDENT');
     $committerName = preg_replace('/\s+<.*/', '',
       rtrim($gitIdent, "\n"));
     preg_match('/<(.*)>/', rtrim($gitIdent, "\n"),
       $gitAuthorEmailMatches);
     $committerEmail = $gitAuthorEmailMatches[1];
 
     // Prepare cURL request to land bot
     $ch = curl_init('https://buildbot.bitcoinabc.org/land');
     curl_setopt($ch, CURLOPT_HTTPHEADER, array(
       'Content-Type:application/json', 'Accept:application/json'));
     curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode(array(
       "committerName" => $committerName,
       "committerEmail" => $committerEmail,
       "revision" => $revision,
       "conduitToken" => $encryptedToken)));
     curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 
     echo phutil_console_format(pht(
       'Pushing revision %s to land bot queue...', $revision) . "\n\n");
 
     $response = curl_exec($ch);
     if (!$response) {
       throw new ArcanistUsageException(pht(
         'Error pushing to land bot queue: %s', curl_error($ch)) . "\n");
     }
 
     $jsonResponse = json_decode($response);
     if (!$jsonResponse) {
       throw new ArcanistUsageException(pht(
         'JSON decoding error: %d', json_last_error()) . "\n");
     }
 
     echo phutil_console_format("<bg:blue>** " .
       pht('Your revision is in the queue:') . " **</bg>\n\n");
     echo phutil_console_format(
       pht('Revision:') . "\thttps://reviews.bitcoinabc.org/%s\n", $revision);
     echo phutil_console_format(pht('Build log:') . "\t%s\n",
       $jsonResponse->webUrl . '&tab=buildLog&guest=1');
 
     curl_close($ch);
     return 0;
   }
 
 }