diff --git a/src/index.php b/src/index.php
index 0f1e650..19781dd 100644
--- a/src/index.php
+++ b/src/index.php
@@ -23,11 +23,11 @@ function transform(string $socketLocation, string $inputFile, string $outputFile
         "blackType" => $blackType,
     ]);
     $json_len = strlen($json);
-    socket_write($socket, pack("J", $json_len), 8);
+    socket_write($socket, pack("Q", $json_len), 8);
     socket_write($socket, $json, $json_len);
     $json_len = "";
     socket_recv($socket, $json_len, 8, MSG_WAITALL);
-    $json_len = unpack("J", $json_len)[1];
+    $json_len = unpack("Q", $json_len)[1];
     $json = "";
     socket_recv($socket, $json, $json_len, MSG_WAITALL);
     $json = json_decode($json, true);