diff --git a/src/applications/config/type/PhabricatorSetConfigType.php b/src/applications/config/type/PhabricatorSetConfigType.php
index 805ae50468..553ee614b8 100644
--- a/src/applications/config/type/PhabricatorSetConfigType.php
+++ b/src/applications/config/type/PhabricatorSetConfigType.php
@@ -1,92 +1,92 @@
 <?php
 
 final class PhabricatorSetConfigType
   extends PhabricatorTextConfigType {
 
   const TYPEKEY = 'set';
 
   protected function newControl(PhabricatorConfigOption $option) {
     return id(new AphrontFormTextAreaControl())
       ->setCaption(pht('Separate values with newlines or commas.'));
   }
 
   protected function newCanonicalValue(
     PhabricatorConfigOption $option,
     $value) {
 
     $value = preg_split('/[\n,]+/', $value);
     foreach ($value as $k => $v) {
       if (!strlen($v)) {
         unset($value[$k]);
       }
       $value[$k] = trim($v);
     }
 
     return array_fill_keys($value, true);
   }
 
   public function newValueFromCommandLineValue(
     PhabricatorConfigOption $option,
     $value) {
 
     try {
       $value = phutil_json_decode($value);
     } catch (Exception $ex) {
       throw $this->newException(
         pht(
           'Option "%s" is of type "%s", but the value you provided is not a '.
           'valid JSON list: when providing a set from the command line, '.
           'specify it as a list of values in JSON. You may need to quote the '.
           'value for your shell (for example: \'["a", "b", ...]\').',
           $option->getKey(),
           $this->getTypeKey()));
     }
 
     if ($value) {
-      if (array_keys($value) !== range(0, count($value) - 1)) {
+      if (!phutil_is_natural_list($value)) {
         throw $this->newException(
           pht(
             'Option "%s" is of type "%s", and should be specified on the '.
             'command line as a JSON list of values. You may need to quote '.
             'the value for your shell (for example: \'["a", "b", ...]\').',
             $option->getKey(),
             $this->getTypeKey()));
       }
     }
 
     return array_fill_keys($value, true);
   }
 
   public function newDisplayValue(
     PhabricatorConfigOption $option,
     $value) {
     return implode("\n", array_keys($value));
   }
 
   public function validateStoredValue(
     PhabricatorConfigOption $option,
     $value) {
 
     if (!is_array($value)) {
       throw $this->newException(
         pht(
           'Option "%s" is of type "%s", but the configured value is not '.
           'a list.',
           $option->getKey(),
           $this->getTypeKey()));
     }
 
     foreach ($value as $k => $v) {
       if ($v !== true) {
         throw $this->newException(
           pht(
             'Option "%s" is of type "%s", but the value at index "%s" of the '.
             'list is not "true".',
             $option->getKey(),
             $this->getTypeKey(),
             $k));
       }
     }
   }
 
 }