diff --git a/src/PhpTokenizer.php b/src/PhpTokenizer.php
index 26f8d203..ef4f9d32 100644
--- a/src/PhpTokenizer.php
+++ b/src/PhpTokenizer.php
@@ -75,7 +75,7 @@ public static function getTokensArrayFromContent(
             $pos += $strlen;
 
             if ($parseContext !== null && !$passedPrefix) {
-                $passedPrefix = \count($prefix) < $pos;
+                $passedPrefix = \strlen($prefix) < $pos;
                 if ($passedPrefix) {
                     $fullStart = $start = $pos = $initialPos;
                 }