diff --git a/src/ASN1/Universal/Integer.php b/src/ASN1/Universal/Integer.php
index bef2891..a799846 100644
--- a/src/ASN1/Universal/Integer.php
+++ b/src/ASN1/Universal/Integer.php
@@ -19,8 +19,8 @@
 
 class Integer extends ASN1Object
 {
-    /** @var int */
-    public $value;
+    /** @var \GMP */
+    private $gmpValue;
 
     /**
      * @param Identifier $identifier
@@ -88,7 +88,29 @@ public static function encodeValue($value): string
 
     public function __toString(): string
     {
-        return (string)$this->value;
+        return gmp_strval($this->gmpValue);
+    }
+
+    public function toGMP(): \GMP
+    {
+        return $this->gmpValue;
+    }
+
+    /**
+     * Magic getter for backward compatibility.
+     * TODO remove in the next major release
+     * Allows access to the old public $value property.
+     *
+     * @param string $name
+     * @return string|null
+     */
+    public function __get(string $name)
+    {
+        if ($name === 'value') {
+            return gmp_strval($this->gmpValue);
+        }
+
+        return null;
     }
 
     public function setValue(Content $content)
@@ -107,9 +129,7 @@ public function setValue(Content $content)
             $number = gmp_sub($number, gmp_pow(2, 8 * $contentLength - 1));
         }
 
-        $value = gmp_strval($number);
-
-        $this->value = $value;
+        $this->gmpValue = $number;
     }
 
     public static function create($integer, $options = []): self
diff --git a/tests/ASN1/Universal/IntegerTest.php b/tests/ASN1/Universal/IntegerTest.php
index b8c3be0..53f0019 100644
--- a/tests/ASN1/Universal/IntegerTest.php
+++ b/tests/ASN1/Universal/IntegerTest.php
@@ -247,4 +247,46 @@ public function testFromBinaryWithOffset()
         $this->assertEquals($originalObject2, $parsedObject);
         $this->assertEquals(9, $offset);
     }
+
+    public function testToGMP()
+    {
+        $object = Integer::create(123);
+        $gmp = $object->toGMP();
+        $this->assertInstanceOf(\GMP::class, $gmp);
+        $this->assertEquals('123', gmp_strval($gmp));
+
+        $object = Integer::create(-456);
+        $gmp = $object->toGMP();
+        $this->assertInstanceOf(\GMP::class, $gmp);
+        $this->assertEquals('-456', gmp_strval($gmp));
+
+        $object = Integer::create(0);
+        $gmp = $object->toGMP();
+        $this->assertInstanceOf(\GMP::class, $gmp);
+        $this->assertEquals('0', gmp_strval($gmp));
+
+        // Test with big integer
+        $bigint = gmp_strval(gmp_pow(2, 128));
+        $object = Integer::create($bigint);
+        $gmp = $object->toGMP();
+        $this->assertInstanceOf(\GMP::class, $gmp);
+        $this->assertEquals($bigint, gmp_strval($gmp));
+    }
+
+    public function testBackwardCompatibilityValueProperty()
+    {
+        $object = Integer::create(123);
+        $this->assertEquals('123', $object->value);
+
+        $object = Integer::create(-456);
+        $this->assertEquals('-456', $object->value);
+
+        $object = Integer::create(0);
+        $this->assertEquals('0', $object->value);
+
+        // Test with big integer
+        $bigint = gmp_strval(gmp_pow(2, 128));
+        $object = Integer::create($bigint);
+        $this->assertEquals($bigint, $object->value);
+    }
 }