diff --git a/phpseclib/Math/BigInteger.php b/phpseclib/Math/BigInteger.php
index b6f2aaf6..2aa39a50 100644
--- a/phpseclib/Math/BigInteger.php
+++ b/phpseclib/Math/BigInteger.php
@@ -2868,8 +2868,7 @@ class BigInteger
         switch (MATH_BIGINTEGER_MODE) {
             case self::MODE_GMP:
                 $temp = new static();
-                $temp->value = gmp_xor($this->value, $x->value);
-
+                $temp->value = gmp_xor(gmp_abs($this->value), gmp_abs($x->value));
                 return $this->_normalize($temp);
             case self::MODE_BCMATH:
                 $left = $this->toBytes();
@@ -2885,6 +2884,7 @@ class BigInteger
 
         $length = max(count($this->value), count($x->value));
         $result = $this->copy();
+        $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 a7a60012..4c88d402 100644
--- a/tests/Unit/Math/BigInteger/TestCase.php
+++ b/tests/Unit/Math/BigInteger/TestCase.php
@@ -209,6 +209,18 @@ 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()