diff --git a/iredis.php b/iredis.php
index a69acf6..0c635eb 100644
--- a/iredis.php
+++ b/iredis.php
@@ -177,7 +177,7 @@ public function readReply()
                 {
                     $bulk_head = trim(fgets($this->connection, 512));
 
-                    if ($size == '-1')
+                    if (substr($bulk_head, 1) == '-1')
                     {
                         $response[] = null;
                     }