diff --git a/src/JWT.php b/src/JWT.php
index 93f6e47d..e9d75639 100644
--- a/src/JWT.php
+++ b/src/JWT.php
@@ -251,7 +251,7 @@ public static function sign(
                 return \hash_hmac($algorithm, $msg, $key, true);
             case 'openssl':
                 $signature = '';
-                if (!openssl_pkey_get_private($key)) {
+                if (!\is_resource($key) && !openssl_pkey_get_private($key)) {
                     throw new DomainException('OpenSSL unable to validate key');
                 }
                 $success = \openssl_sign($msg, $signature, $key, $algorithm); // @phpstan-ignore-line