diff --git a/src/Symfony/Component/Debug/Tests/Exception/FlattenExceptionTest.php b/src/Symfony/Component/Debug/Tests/Exception/FlattenExceptionTest.php
index 8fd1c79594d38..cac285a5a4962 100644
--- a/src/Symfony/Component/Debug/Tests/Exception/FlattenExceptionTest.php
+++ b/src/Symfony/Component/Debug/Tests/Exception/FlattenExceptionTest.php
@@ -256,7 +256,7 @@ function () {},
 
         // assertEquals() does not like NAN values.
         $this->assertEquals($array[$i][0], 'float');
-        $this->assertTrue(is_nan($array[$i++][1]));
+        $this->assertNan($array[$i][1]);
     }
 
     public function testRecursionInArguments()