diff --git a/src/Framework/Constraint/StringStartsWith.php b/src/Framework/Constraint/StringStartsWith.php
index 0d54dcb0e90..a169d94f44f 100644
--- a/src/Framework/Constraint/StringStartsWith.php
+++ b/src/Framework/Constraint/StringStartsWith.php
@@ -26,7 +26,7 @@ public function __construct(string $prefix)
     {
         parent::__construct();
 
-        if (strlen($prefix) === 0) {
+        if (\strlen($prefix) === 0) {
             throw InvalidArgumentHelper::factory(1, 'non-empty string');
         }