diff --git a/src/applications/differential/conduit/ConduitAPI_differential_getcommitmessage_Method.php b/src/applications/differential/conduit/ConduitAPI_differential_getcommitmessage_Method.php
index 287c620732..7b0b7a9511 100644
--- a/src/applications/differential/conduit/ConduitAPI_differential_getcommitmessage_Method.php
+++ b/src/applications/differential/conduit/ConduitAPI_differential_getcommitmessage_Method.php
@@ -1,194 +1,192 @@
 <?php
 
 final class ConduitAPI_differential_getcommitmessage_Method
   extends ConduitAPIMethod {
 
   public function getMethodDescription() {
     return "Retrieve Differential commit messages or message templates.";
   }
 
   public function defineParamTypes() {
     return array(
       'revision_id' => 'optional revision_id',
       'fields' => 'optional dict<string, wild>',
       'edit' => 'optional enum<"edit", "create">',
     );
   }
 
   public function defineReturnType() {
     return 'nonempty string';
   }
 
   public function defineErrorTypes() {
     return array(
       'ERR_NOT_FOUND' => 'Revision was not found.',
     );
   }
 
   protected function execute(ConduitAPIRequest $request) {
     $id = $request->getValue('revision_id');
     $viewer = $request->getUser();
 
     if ($id) {
       $revision = id(new DifferentialRevisionQuery())
         ->withIDs(array($id))
         ->setViewer($viewer)
         ->needReviewerStatus(true)
         ->needActiveDiffs(true)
         ->executeOne();
       if (!$revision) {
         throw new ConduitException('ERR_NOT_FOUND');
       }
     } else {
       $revision = DifferentialRevision::initializeNewRevision($viewer);
       $revision->attachReviewerStatus(array());
       $revision->attachActiveDiff(null);
     }
 
     $is_edit = $request->getValue('edit');
     $is_create = ($is_edit == 'create');
 
     $field_list = PhabricatorCustomField::getObjectFields(
       $revision,
       ($is_edit
         ? DifferentialCustomField::ROLE_COMMITMESSAGEEDIT
         : DifferentialCustomField::ROLE_COMMITMESSAGE));
 
     $field_list
       ->setViewer($viewer)
       ->readFieldsFromStorage($revision);
 
     $field_map = mpull($field_list->getFields(), null, 'getFieldKeyForConduit');
 
     if ($is_edit) {
       $fields = $request->getValue('fields', array());
       foreach ($fields as $field => $value) {
         $custom_field = idx($field_map, $field);
         if (!$custom_field) {
-          throw new Exception(
-            pht(
-              'Commit message includes field "%s", but this field does not '.
-              'correspond to a known field.',
-              $field));
+          // Just ignore this, these workflows don't make strong distictions
+          // about field editability on the client side.
+          continue;
         }
         if ($is_create ||
             $custom_field->shouldOverwriteWhenCommitMessageIsEdited()) {
           $custom_field->readValueFromCommitMessage($value);
         }
       }
     }
 
     $phids = array();
     foreach ($field_list->getFields() as $key => $field) {
       $field_phids = $field->getRequiredHandlePHIDsForCommitMessage();
       if (!is_array($field_phids)) {
         throw new Exception(
           pht(
             'Custom field "%s" was expected to return an array of handle '.
             'PHIDs required for commit message rendering, but returned "%s" '.
             'instead.',
             $field->getFieldKey(),
             gettype($field_phids)));
       }
       $phids[$key] = $field_phids;
     }
 
     $all_phids = array_mergev($phids);
     if ($all_phids) {
       $all_handles = id(new PhabricatorHandleQuery())
         ->setViewer($viewer)
         ->withPHIDs($all_phids)
         ->execute();
     } else {
       $all_handles = array();
     }
 
     $key_title = id(new DifferentialTitleField())->getFieldKey();
     $default_title = DifferentialTitleField::getDefaultTitle();
 
     $commit_message = array();
     foreach ($field_list->getFields() as $key => $field) {
       $handles = array_select_keys($all_handles, $phids[$key]);
 
       $label = $field->renderCommitMessageLabel();
       $value = $field->renderCommitMessageValue($handles);
 
       if (!is_string($value) && !is_null($value)) {
         throw new Exception(
           pht(
             'Custom field "%s" was expected to render a string or null value, '.
             'but rendered a "%s" instead.',
             $field->getFieldKey(),
             gettype($value)));
       }
 
       $is_title = ($key == $key_title);
 
       if (!strlen($value)) {
         if ($is_title) {
           $commit_message[] = $default_title;
         } else {
           if ($is_edit && $field->shouldAppearInCommitMessageTemplate()) {
             $commit_message[] = $label.': ';
           }
         }
       } else {
         if ($is_title) {
           $commit_message[] = $value;
         } else {
           $value = str_replace(
             array("\r\n", "\r"),
             array("\n",   "\n"),
             $value);
           if (strpos($value, "\n") !== false || substr($value, 0, 2) === '  ') {
             $commit_message[] = "{$label}:\n{$value}";
           } else {
             $commit_message[] = "{$label}: {$value}";
           }
         }
       }
     }
 
     if ($is_edit) {
       $tip = $this->getProTip($field_list);
       if ($tip !== null) {
         $commit_message[] = "\n".$tip;
       }
     }
 
     $commit_message = implode("\n\n", $commit_message);
 
     return $commit_message;
   }
 
   private function getProTip() {
     // Any field can provide tips, whether it normally appears on commit
     // messages or not.
     $field_list = PhabricatorCustomField::getObjectFields(
       new DifferentialRevision(),
       PhabricatorCustomField::ROLE_DEFAULT);
 
     $tips = array();
     foreach ($field_list->getFields() as $key => $field) {
       $tips[] = $field->getProTips();
     }
     $tips = array_mergev($tips);
 
     if (!$tips) {
       return null;
     }
 
     shuffle($tips);
 
     $tip = pht('Tip: %s', head($tips));
     $tip = wordwrap($tip, 78, "\n", true);
 
     $lines = explode("\n", $tip);
     foreach ($lines as $key => $line) {
       $lines[$key] = "# ".$line;
     }
 
     return implode("\n", $lines);
   }
 
 }