diff --git a/src/lint/linter/ArcanistPyFlakesLinter.php b/src/lint/linter/ArcanistPyFlakesLinter.php
index 19740a1e..fe047c50 100644
--- a/src/lint/linter/ArcanistPyFlakesLinter.php
+++ b/src/lint/linter/ArcanistPyFlakesLinter.php
@@ -1,102 +1,106 @@
 <?php
 
 /**
  * Uses "PyFlakes" to detect various errors in Python code.
  */
 final class ArcanistPyFlakesLinter extends ArcanistExternalLinter {
 
   public function getInfoURI() {
     return 'https://pypi.python.org/pypi/pyflakes';
   }
 
   public function getInfoName() {
     return pht('PyFlakes');
   }
 
   public function getInfoDescription() {
     return pht(
       'PyFlakes is a simple program which checks Python source files for '.
       'errors.');
   }
 
   public function getLinterName() {
     return 'PYFLAKES';
   }
 
   public function getLinterConfigurationName() {
     return 'pyflakes';
   }
 
   public function getDefaultBinary() {
     $prefix = $this->getDeprecatedConfiguration('lint.pyflakes.prefix');
     $bin = $this->getDeprecatedConfiguration('lint.pyflakes.bin', 'pyflakes');
 
     if ($prefix) {
       return $prefix.'/'.$bin;
     } else {
       return $bin;
     }
   }
 
   public function getVersion() {
     list($stdout) = execx('%C --version', $this->getExecutableCommand());
 
     $matches = array();
     if (preg_match('/^(?P<version>\d+\.\d+\.\d+)$/', $stdout, $matches)) {
       return $matches['version'];
     } else {
       return false;
     }
   }
 
   public function getInstallInstructions() {
     return pht('Install pyflakes with `pip install pyflakes`.');
   }
 
   public function shouldExpectCommandErrors() {
     return true;
   }
 
   public function supportsReadDataFromStdin() {
     return true;
   }
 
   protected function parseLinterOutput($path, $err, $stdout, $stderr) {
     $lines = phutil_split_lines($stdout, false);
 
     $messages = array();
     foreach ($lines as $line) {
       $matches = null;
       if (!preg_match('/^(.*?):(\d+): (.*)$/', $line, $matches)) {
         continue;
       }
       foreach ($matches as $key => $match) {
         $matches[$key] = trim($match);
       }
 
       $severity = ArcanistLintSeverity::SEVERITY_WARNING;
       $description = $matches[3];
 
       $error_regexp = '/(^undefined|^duplicate|before assignment$)/';
       if (preg_match($error_regexp, $description)) {
         $severity = ArcanistLintSeverity::SEVERITY_ERROR;
       }
 
       $message = new ArcanistLintMessage();
       $message->setPath($path);
       $message->setLine($matches[2]);
       $message->setCode($this->getLinterName());
       $message->setDescription($description);
       $message->setSeverity($severity);
 
       $messages[] = $message;
     }
 
     if ($err && !$messages) {
       return false;
     }
 
     return $messages;
   }
 
+  protected function canCustomizeLintSeverities() {
+    return false;
+  }
+
 }