diff --git a/src/PassportServiceProvider.php b/src/PassportServiceProvider.php
index daeb04422..0418d43ca 100644
--- a/src/PassportServiceProvider.php
+++ b/src/PassportServiceProvider.php
@@ -265,7 +265,7 @@ protected function registerResourceServer()
      */
     protected function makeCryptKey($type)
     {
-        $key = str_replace('\\n', "\n", $this->app->make(Config::class)->get('passport.'.$type.'_key'));
+        $key = str_replace('\\n', "\n", $this->app->make(Config::class)->get('passport.'.$type.'_key') ?? '');
 
         if (! $key) {
             $key = 'file://'.Passport::keyPath('oauth-'.$type.'.key');