diff --git a/src/lint/linter/ArcanistClosureLinter.php b/src/lint/linter/ArcanistClosureLinter.php
--- a/src/lint/linter/ArcanistClosureLinter.php
+++ b/src/lint/linter/ArcanistClosureLinter.php
@@ -17,6 +17,20 @@
     return pht("Uses Google's Closure Linter to check Javascript code.");
   }
 
+  protected function getLintCodeFromLinterConfigurationKey($code) {
+    if (!preg_match('/^(E:|W:)\d+$/', $code)) {
+      throw new Exception(
+        pht(
+          'Unrecognized lint message code "%s". Expected a valid gJSLint'.
+          'lint code like "%s" or "%s".',
+          $code,
+          'E:0110',
+          'W:0010')
+      );
+    }
+    return $code;
+  }
+
   public function getLinterName() {
     return 'Closure Linter';
   }
@@ -29,6 +43,14 @@
     return 'gjslint';
   }
 
+  protected function getDefaultMessageSeverity($code) {
+    if (preg_match('/^W/', $code)) {
+      return ArcanistLintSeverity::SEVERITY_WARNING;
+    } else {
+      return ArcanistLintSeverity::SEVERITY_ERROR;
+    }
+  }
+
   public function getInstallInstructions() {
     return pht(
       'Install gJSLint using `sudo easy_install http://closure-linter'.
@@ -47,8 +69,6 @@
     // Each line looks like this:
     // Line 46, E:0110: Line too long (87 characters).
     $regex = '/^Line (\d+), (E:\d+): (.*)/';
-    $severity_code = ArcanistLintSeverity::SEVERITY_ERROR;
-
     $lines = phutil_split_lines($stdout, false);
 
     $messages = array();
@@ -68,7 +88,7 @@
       $message->setName($matches[2]);
       $message->setCode($this->getLinterName());
       $message->setDescription($matches[3]);
-      $message->setSeverity($severity_code);
+      $message->setSeverity($this->getLintMessageSeverity($matches[2]));
 
       $messages[] = $message;
     }