diff --git a/tests/ShortcutTest.php b/tests/ShortcutTest.php
index e5fa1d4..dd52381 100644
--- a/tests/ShortcutTest.php
+++ b/tests/ShortcutTest.php
@@ -23,9 +23,10 @@ public function testHelper(): void
 
     private function testDefer(int &$foo): void
     {
-        defer(function () use (&$foo) {
+        $_ = defer(function () use (&$foo) {
             $foo++;
         });
+        $this->assertSame(0, $foo);
     }
 }