diff --git a/src/applications/config/check/PhabricatorPHPPreflightSetupCheck.php b/src/applications/config/check/PhabricatorPHPPreflightSetupCheck.php
index 65a582b29c..82a13438d8 100644
--- a/src/applications/config/check/PhabricatorPHPPreflightSetupCheck.php
+++ b/src/applications/config/check/PhabricatorPHPPreflightSetupCheck.php
@@ -1,201 +1,139 @@
 <?php
 
 final class PhabricatorPHPPreflightSetupCheck extends PhabricatorSetupCheck {
 
   public function getDefaultGroup() {
     return self::GROUP_PHP;
   }
 
   public function isPreflightCheck() {
     return true;
   }
 
   protected function executeChecks() {
     if (version_compare(phpversion(), 7, '>=')) {
       $message = pht(
         'This version of Phabricator does not support PHP 7. You '.
         'are running PHP %s.',
         phpversion());
 
       $this->newIssue('php.version7')
         ->setIsFatal(true)
         ->setName(pht('PHP 7 Not Supported'))
         ->setMessage($message)
         ->addLink(
           'https://phurl.io/u/php7',
           pht('Phabricator PHP 7 Compatibility Information'));
 
       return;
     }
 
     $safe_mode = ini_get('safe_mode');
     if ($safe_mode) {
       $message = pht(
         "You have '%s' enabled in your PHP configuration, but Phabricator ".
         "will not run in safe mode. Safe mode has been deprecated in PHP 5.3 ".
         "and removed in PHP 5.4.\n\nDisable safe mode to continue.",
         'safe_mode');
 
       $this->newIssue('php.safe_mode')
         ->setIsFatal(true)
         ->setName(pht('Disable PHP %s', 'safe_mode'))
         ->setMessage($message)
         ->addPHPConfig('safe_mode');
       return;
     }
 
     // Check for `disable_functions` or `disable_classes`. Although it's
     // possible to disable a bunch of functions (say, `array_change_key_case()`)
     // and classes and still have Phabricator work fine, it's unreasonably
     // difficult for us to be sure we'll even survive setup if these options
     // are enabled. Phabricator needs access to the most dangerous functions,
     // so there is no reasonable configuration value here which actually
     // provides a benefit while guaranteeing Phabricator will run properly.
 
     $disable_options = array('disable_functions', 'disable_classes');
     foreach ($disable_options as $disable_option) {
       $disable_value = ini_get($disable_option);
       if ($disable_value) {
 
         // By default Debian installs the pcntl extension but disables all of
         // its functions using configuration. Whitelist disabling these
         // functions so that Debian PHP works out of the box (we do not need to
         // call these functions from the web UI). This is pretty ridiculous but
         // it's not the users' fault and they haven't done anything crazy to
         // get here, so don't make them pay for Debian's unusual choices.
         // See: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=605571
         $fatal = true;
         if ($disable_option == 'disable_functions') {
           $functions = preg_split('/[, ]+/', $disable_value);
           $functions = array_filter($functions);
           foreach ($functions as $k => $function) {
             if (preg_match('/^pcntl_/', $function)) {
               unset($functions[$k]);
             }
           }
           if (!$functions) {
             $fatal = false;
           }
         }
 
         if ($fatal) {
           $message = pht(
             "You have '%s' enabled in your PHP configuration.\n\n".
             "This option is not compatible with Phabricator. Remove ".
             "'%s' from your configuration to continue.",
             $disable_option,
             $disable_option);
 
           $this->newIssue('php.'.$disable_option)
             ->setIsFatal(true)
             ->setName(pht('Remove PHP %s', $disable_option))
             ->setMessage($message)
             ->addPHPConfig($disable_option);
         }
       }
     }
 
     $overload_option = 'mbstring.func_overload';
     $func_overload = ini_get($overload_option);
     if ($func_overload) {
       $message = pht(
         "You have '%s' enabled in your PHP configuration.\n\n".
         "This option is not compatible with Phabricator. Disable ".
         "'%s' in your PHP configuration to continue.",
         $overload_option,
         $overload_option);
 
       $this->newIssue('php'.$overload_option)
         ->setIsFatal(true)
         ->setName(pht('Disable PHP %s', $overload_option))
         ->setMessage($message)
         ->addPHPConfig($overload_option);
     }
 
     $open_basedir = ini_get('open_basedir');
-    if ($open_basedir) {
+    if (strlen($open_basedir)) {
+      // If `open_basedir` is set, just fatal. It's technically possible for
+      // us to run with certain values of `open_basedir`, but: we can only
+      // raise fatal errors from preflight steps, so we'd have to do this check
+      // in two parts to support fatal and advisory versions; it's much simpler
+      // to just fatal instead of trying to test all the different things we
+      // may need to access in the filesystem; and use of this option seems
+      // rare (particularly in supported environments).
 
-      // 'open_basedir' restricts which files we're allowed to access with
-      // file operations. This might be okay -- we don't need to write to
-      // arbitrary places in the filesystem -- but we need to access certain
-      // resources. This setting is unlikely to be providing any real measure
-      // of security so warn even if things look OK.
-
-      $failures = array();
-
-      try {
-        $open_libphutil = class_exists('Future');
-      } catch (Exception $ex) {
-        $failures[] = $ex->getMessage();
-      }
-
-      try {
-        $open_arcanist = class_exists('ArcanistDiffParser');
-      } catch (Exception $ex) {
-        $failures[] = $ex->getMessage();
-      }
-
-      $open_urandom = false;
-      try {
-        Filesystem::readRandomBytes(1);
-        $open_urandom = true;
-      } catch (FilesystemException $ex) {
-        $failures[] = $ex->getMessage();
-      }
-
-      try {
-        $tmp = new TempFile();
-        file_put_contents($tmp, '.');
-        $open_tmp = @fopen((string)$tmp, 'r');
-        if (!$open_tmp) {
-          $failures[] = pht(
-            "Unable to read temporary file '%s'.",
-            (string)$tmp);
-        }
-      } catch (Exception $ex) {
-        $message = $ex->getMessage();
-        $dir = sys_get_temp_dir();
-        $failures[] = pht(
-          "Unable to open temp files from '%s': %s",
-          $dir,
-          $message);
-      }
+      $message = pht(
+        "Your server is configured with '%s', which prevents Phabricator ".
+        "from opening files it requires access to.\n\n".
+        "Disable this setting to continue.",
+        'open_basedir');
 
       $issue = $this->newIssue('php.open_basedir')
         ->setName(pht('Disable PHP %s', 'open_basedir'))
-        ->addPHPConfig('open_basedir');
-
-      if ($failures) {
-        $message = pht(
-          "Your server is configured with '%s', which prevents Phabricator ".
-          "from opening files it requires access to.\n\n".
-          "Disable this setting to continue.\n\nFailures:\n\n%s",
-          'open_basedir',
-          implode("\n\n", $failures));
-
-        $issue
-          ->setIsFatal(true)
-          ->setMessage($message);
-
-        return;
-      } else {
-        $summary = pht(
-          "You have '%s' configured in your PHP settings, which ".
-          "may cause some features to fail.",
-          'open_basedir');
-
-        $message = pht(
-          "You have '%s' configured in your PHP settings. Although this ".
-          "setting appears permissive enough that Phabricator will work ".
-          "properly, you may still run into problems because of it.\n\n".
-          "Consider disabling '%s'.",
-          'open_basedir',
-          'open_basedir');
-
-        $issue
-          ->setSummary($summary)
-          ->setMessage($message);
-      }
+        ->addPHPConfig('open_basedir')
+        ->setIsFatal(true)
+        ->setMessage($message);
     }
+
   }
 }