diff --git a/phpseclib/Math/BigInteger.php b/phpseclib/Math/BigInteger.php
index 1ca135aa..a9163b2b 100644
--- a/phpseclib/Math/BigInteger.php
+++ b/phpseclib/Math/BigInteger.php
@@ -232,7 +232,7 @@ class BigInteger implements \Serializable
      */
     function toBits($twos_compliment = false)
     {
-        return $this->value->toBits();
+        return $this->value->toBits($twos_compliment);
     }
 
     /**