diff --git a/phpseclib/Math/BigInteger/Engines/PHP.php b/phpseclib/Math/BigInteger/Engines/PHP.php
index 19e7a1f1..5ad7b7fc 100644
--- a/phpseclib/Math/BigInteger/Engines/PHP.php
+++ b/phpseclib/Math/BigInteger/Engines/PHP.php
@@ -1315,7 +1315,7 @@ abstract class PHP extends Engine
                 break;
             }
         }
-        $s = static::BASE * $i + $j - 1;
+        $s = static::BASE * $i + $j;
         $r->rshift($s);
         return $s;
     }