diff --git a/phpseclib/Math/BigInteger.php b/phpseclib/Math/BigInteger.php
index 969c9ad6..32afa7a0 100644
--- a/phpseclib/Math/BigInteger.php
+++ b/phpseclib/Math/BigInteger.php
@@ -550,7 +550,7 @@ class Math_BigInteger
             $temp = $comparison < 0 ? $this->add(new Math_BigInteger(1)) : $this->copy();
             $bytes = $temp->toBytes();
 
-            if (empty($bytes)) { // eg. if the number we're trying to convert is -1
+            if (!strlen($bytes)) { // eg. if the number we're trying to convert is -1
                 $bytes = chr(0);
             }