diff --git a/src/CryptKey.php b/src/CryptKey.php
index 935461cc..0d5f5cf6 100644
--- a/src/CryptKey.php
+++ b/src/CryptKey.php
@@ -14,7 +14,7 @@ namespace League\OAuth2\Server;
 class CryptKey
 {
     const RSA_KEY_PATTERN =
-        '/^(-----BEGIN (RSA )?(PUBLIC|PRIVATE) KEY-----).+(-----END (RSA )?(PUBLIC|PRIVATE) KEY-----)\s*$/s';
+        '/^(-----BEGIN (RSA )?(PUBLIC|PRIVATE) KEY-----)\R.*(-----END (RSA )?(PUBLIC|PRIVATE) KEY-----)\R?$/s';
 
     /**
      * @var string