diff --git a/scripts/init/lib.php b/scripts/init/lib.php
index 0b756b7c32..659c50802d 100644
--- a/scripts/init/lib.php
+++ b/scripts/init/lib.php
@@ -28,5 +28,8 @@ function init_phabricator_script(array $options) {
   phutil_load_library(dirname(__FILE__).'/../../src/');
 
   $config_optional = $options['config.optional'];
-  PhabricatorEnv::initializeScriptEnvironment($config_optional);
+  $no_extensions = $options['no-extensions'] ?? false;
+  PhabricatorEnv::initializeScriptEnvironment(
+    $config_optional,
+    $no_extensions);
 }
diff --git a/src/infrastructure/env/PhabricatorEnv.php b/src/infrastructure/env/PhabricatorEnv.php
index 15f6efe22c..04f6b632e6 100644
--- a/src/infrastructure/env/PhabricatorEnv.php
+++ b/src/infrastructure/env/PhabricatorEnv.php
@@ -68,11 +68,13 @@ final class PhabricatorEnv extends Phobject {
    * @phutil-external-symbol class PhabricatorStartup
    */
   public static function initializeWebEnvironment() {
-    self::initializeCommonEnvironment(false);
+    self::initializeCommonEnvironment(false, false);
   }
 
-  public static function initializeScriptEnvironment($config_optional) {
-    self::initializeCommonEnvironment($config_optional);
+  public static function initializeScriptEnvironment(
+    $config_optional,
+    $no_extensions) {
+    self::initializeCommonEnvironment($config_optional, $no_extensions);
 
     // NOTE: This is dangerous in general, but we know we're in a script context
     // and are not vulnerable to CSRF.
@@ -88,11 +90,13 @@ final class PhabricatorEnv extends Phobject {
   }
 
 
-  private static function initializeCommonEnvironment($config_optional) {
+  private static function initializeCommonEnvironment(
+    $config_optional,
+    $no_extensions) {
     PhutilErrorHandler::initialize();
 
     self::resetUmask();
-    self::buildConfigurationSourceStack($config_optional);
+    self::buildConfigurationSourceStack($config_optional, $no_extensions);
 
     // Force a valid timezone. If both PHP and Phabricator configuration are
     // invalid, use UTC.
@@ -179,7 +183,8 @@ final class PhabricatorEnv extends Phobject {
     }
   }
 
-  private static function buildConfigurationSourceStack($config_optional) {
+  private static function buildConfigurationSourceStack(
+    $config_optional, $no_extensions) {
     self::dropConfigCache();
 
     $stack = new PhabricatorConfigStackSource();
@@ -203,8 +208,10 @@ final class PhabricatorEnv extends Phobject {
     // If the install overrides the database adapter, we might need to load
     // the database adapter class before we can push on the database config.
     // This config is locked and can't be edited from the web UI anyway.
-    foreach (self::getEnvConfig('load-libraries') as $library) {
-      phutil_load_library($library);
+    if (!$no_extensions) {
+      foreach (self::getEnvConfig('load-libraries') as $library) {
+        phutil_load_library($library);
+      }
     }
 
     // Drop any class map caches, since they will have generated without
diff --git a/src/infrastructure/testing/PhabricatorTestCase.php b/src/infrastructure/testing/PhabricatorTestCase.php
index 64dc22d366..10302733c1 100644
--- a/src/infrastructure/testing/PhabricatorTestCase.php
+++ b/src/infrastructure/testing/PhabricatorTestCase.php
@@ -57,9 +57,18 @@ abstract class PhabricatorTestCase extends PhutilTestCase {
     return $config;
   }
 
+  /** @phutil-external-symbol function init_phabricator_script */
   public function willRunTestCases(array $test_cases) {
     $root = dirname(phutil_get_library_root('phabricator'));
-    require_once $root.'/scripts/__init_script__.php';
+    if (!function_exists('init_phabricator_script')) {
+      // Run the initialization routines only if nothing else already did
+      require_once $root.'/scripts/init/lib.php';
+      init_phabricator_script(
+        array(
+        'config.optional' => false,
+        'no-extensions' => true,
+      ));
+    }
 
     $config = $this->getComputedConfiguration();