diff --git a/tests/Assert/Tests/Fixtures/PR142_OverrideStringify.php b/tests/Assert/Tests/Fixtures/PR142_OverrideStringify.php
index 154ff721..d06670fa 100644
--- a/tests/Assert/Tests/Fixtures/PR142_OverrideStringify.php
+++ b/tests/Assert/Tests/Fixtures/PR142_OverrideStringify.php
@@ -18,7 +18,7 @@
 
 class PR142_OverrideStringify extends Assertion
 {
-    protected static function stringify($value)
+    protected static function stringify($value): string
     {
         return '***'.parent::stringify($value).'***';
     }