diff --git a/src/lint/linter/ArcanistPEP8Linter.php b/src/lint/linter/ArcanistPEP8Linter.php
index bb93acb4..0b19006d 100644
--- a/src/lint/linter/ArcanistPEP8Linter.php
+++ b/src/lint/linter/ArcanistPEP8Linter.php
@@ -109,12 +109,7 @@ final class ArcanistPEP8Linter extends ArcanistExternalLinter {
     if (preg_match('/^W/', $code)) {
       return ArcanistLintSeverity::SEVERITY_WARNING;
     } else {
-
-      // TODO: Once severities/.arclint are more usable, restore this to
-      // "ERROR".
-      // return ArcanistLintSeverity::SEVERITY_ERROR;
-
-      return ArcanistLintSeverity::SEVERITY_WARNING;
+      return ArcanistLintSeverity::SEVERITY_ERROR;
     }
   }
 
diff --git a/src/lint/linter/__tests__/pep8/imports.lint-test b/src/lint/linter/__tests__/pep8/imports.lint-test
index 54ef8efd..cd9b2287 100644
--- a/src/lint/linter/__tests__/pep8/imports.lint-test
+++ b/src/lint/linter/__tests__/pep8/imports.lint-test
@@ -1,3 +1,3 @@
 import os, sys
 ~~~~~~~~~~
-warning:1:10
+error:1:10