diff --git a/sapi/fpm/tests/bug77780-header-sent-error.phpt b/sapi/fpm/tests/bug77780-header-sent-error.phpt
index b5e76918547..017a2aa513c 100644
--- a/sapi/fpm/tests/bug77780-header-sent-error.phpt
+++ b/sapi/fpm/tests/bug77780-header-sent-error.phpt
@@ -24,7 +24,7 @@ echo str_repeat('asdfghjkl', 150000) . "\n";
 EOT;
 
 $tester = new FPM\Tester($cfg, $code);
-$tester->start();
+$tester->start(extensions: ['session']);
 $tester->expectLogStartNotices();
 $tester
     ->request(
diff --git a/sapi/fpm/tests/tester.inc b/sapi/fpm/tests/tester.inc
index 0bb114e8597..ae60114f78f 100644
--- a/sapi/fpm/tests/tester.inc
+++ b/sapi/fpm/tests/tester.inc
@@ -379,12 +379,17 @@ class Tester
      * @param array $extraArgs   Command extra arguments.
      * @param bool  $forceStderr Whether to output to stderr so error log is used.
      * @param bool  $daemonize   Whether to start FPM daemonized
+     * @param array $extensions  List of extension to add if shared build used.
      *
      * @return bool
      * @throws \Exception
      */
-    public function start(array $extraArgs = [], bool $forceStderr = true, bool $daemonize = false)
-    {
+    public function start(
+        array $extraArgs = [],
+        bool $forceStderr = true,
+        bool $daemonize = false,
+        array $extensions = []
+    ) {
         $configFile = $this->createConfig();
         $desc       = $this->outDesc ? [] : [1 => array('pipe', 'w'), 2 => array('redirect', 1)];
 
@@ -399,6 +404,14 @@ class Tester
             $cmd[] = '-F';
         }
 
+        $extensionDir = getenv('TEST_FPM_EXTENSION_DIR');
+        if ($extensionDir) {
+            $cmd[] = '-dextension_dir=' . $extensionDir;
+            foreach ($extensions as $extension) {
+                $cmd[] = '-dextension=' . $extension;
+            }
+        }
+
         if (getenv('TEST_FPM_RUN_AS_ROOT')) {
             $cmd[] = '--allow-to-run-as-root';
         }