diff --git a/tests/PhpUnitSfTestHelperTrait.php b/tests/PhpUnitSfTestHelperTrait.php
index 49cd0e754..eaba6b4e6 100644
--- a/tests/PhpUnitSfTestHelperTrait.php
+++ b/tests/PhpUnitSfTestHelperTrait.php
@@ -49,7 +49,7 @@ public function isa_ok($actual, $expected, string $message = ''): void
     {
         if ('array' === $expected) {
             $this->assertIsArray($actual, $message);
-        } elseif (str_starts_with($expected, 'sf')) {
+        } elseif (strpos($expected, 'sf') === 0) {
             $this->assertInstanceOf($expected, $actual, $message);
         } else {
             throw new \RuntimeException('unhandled type: '.$expected);