diff --git a/test/ComposerRequireCheckerTest/DependencyGuesser/DependencyGuesserTest.php b/test/ComposerRequireCheckerTest/DependencyGuesser/DependencyGuesserTest.php
index 066dabe8..7341cc0e 100644
--- a/test/ComposerRequireCheckerTest/DependencyGuesser/DependencyGuesserTest.php
+++ b/test/ComposerRequireCheckerTest/DependencyGuesser/DependencyGuesserTest.php
@@ -9,6 +9,7 @@
 use PHPUnit\Framework\TestCase;
 
 use function extension_loaded;
+use function iterator_to_array;
 
 final class DependencyGuesserTest extends TestCase
 {
@@ -25,7 +26,7 @@ public function testGuessExtJson(): void
             $this->markTestSkipped('extension json is not available');
         }
 
-        $result = $this->guesser->__invoke('json_decode');
+        $result = iterator_to_array($this->guesser->__invoke('json_decode'));
         $this->assertNotEmpty($result);
         $this->assertContains('ext-json', $result);
     }
@@ -40,7 +41,7 @@ public function testCoreExtensionsResolvesToPHP(): void
     {
         $options       = new Options(['php-core-extensions' => ['SPL', 'something-else']]);
         $this->guesser = new DependencyGuesser($options);
-        $result        = $this->guesser->__invoke('RecursiveDirectoryIterator');
+        $result        = iterator_to_array($this->guesser->__invoke('RecursiveDirectoryIterator'));
         $this->assertNotEmpty($result);
         $this->assertContains('php', $result);
     }