diff --git a/phpseclib/Math/BigInteger/Engines/GMP.php b/phpseclib/Math/BigInteger/Engines/GMP.php
index cdabbb72..17696c17 100644
--- a/phpseclib/Math/BigInteger/Engines/GMP.php
+++ b/phpseclib/Math/BigInteger/Engines/GMP.php
@@ -387,7 +387,7 @@ class GMP extends Engine
     public function bitwise_xor(GMP $x)
     {
         $temp = new self();
-        $temp->value = $this->value ^ $x->value;
+        $temp->value = gmp_abs($this->value) ^ gmp_abs($x->value);
 
         return $this->normalize($temp);
     }
diff --git a/phpseclib/Math/BigInteger/Engines/PHP.php b/phpseclib/Math/BigInteger/Engines/PHP.php
index 7ed704eb..1ec77e24 100644
--- a/phpseclib/Math/BigInteger/Engines/PHP.php
+++ b/phpseclib/Math/BigInteger/Engines/PHP.php
@@ -938,6 +938,7 @@ abstract class PHP extends Engine
     {
         $length = max(count($this->value), count($x->value));
         $result = clone $this;
+        $result->is_negative = false;
         $result->value = array_pad($result->value, $length, 0);
         $x->value = array_pad($x->value, $length, 0);
 
diff --git a/tests/Unit/Math/BigInteger/TestCase.php b/tests/Unit/Math/BigInteger/TestCase.php
index 174b008a..55637e45 100644
--- a/tests/Unit/Math/BigInteger/TestCase.php
+++ b/tests/Unit/Math/BigInteger/TestCase.php
@@ -198,6 +198,18 @@ abstract class Unit_Math_BigInteger_TestCase extends PhpseclibTestCase
         $z = $this->getInstance('BC98BC98BC98BC98BC98BC98', 16);
 
         $this->assertSame($z->toHex(), $x->bitwise_XOR($y)->toHex());
+
+        // @group github1245
+
+        $a = $this->getInstance(1);
+        $b = $this->getInstance(-2);
+        $c = $a->bitwise_xor($b);
+        $this->assertSame("$c", '3');
+
+        $a = $this->getInstance('-6725760161961546982');
+        $b = $this->getInstance(51);
+        $c = $a->bitwise_xor($b);
+        $this->assertSame("$c", '6725760161961546965');
     }
 
     public function testBitwiseNOT()