diff --git a/src/Buffertools/Parser.php b/src/Buffertools/Parser.php
index 5ca477c..22d1af2 100644
--- a/src/Buffertools/Parser.php
+++ b/src/Buffertools/Parser.php
@@ -30,14 +30,12 @@ class Parser
      */
     public function __construct(BufferInterface $input = null)
     {
-        $this->position = 0;
-
-        if (null === $input) {
-            $this->string = '';
-            $this->size = 0;
-        } else {
+        if ($input instanceof BufferInterface) {
             $this->string = $input->getBinary();
             $this->size = $input->getSize();
+        } else {
+            $this->string = '';
+            $this->size = 0;
         }
     }