Minor correction

src/SignatureAlgorithm/RSA/RSA.php

@@ -17,12 +17,20 @@
 use Jose\Component\Core\JWK;
 use Jose\Component\Core\Util\RSAKey;
 use Jose\Component\Signature\Algorithm\Util\RSA as JoseRSA;
+use RuntimeException;
 
 /**
  * @deprecated Please use either RSAPSS or RSAPKCS1 depending on the padding mode
  */
 abstract class RSA implements SignatureAlgorithm
 {
+    public function __construct()
+    {
+        if (!\extension_loaded('gmp')) {
+            throw new RuntimeException(static::class.' requires gmp extension');
+        }
+    }
+
     public function allowedKeyTypes(): array
     {
         return ['RSA'];