diff --git a/src/Mpesa/Auth/Authenticator.php b/src/Mpesa/Auth/Authenticator.php
index 96cad4e..1c99314 100755
--- a/src/Mpesa/Auth/Authenticator.php
+++ b/src/Mpesa/Auth/Authenticator.php
@@ -116,7 +116,8 @@ private function makeRequest($key, $secret)
      */
     private function saveCredentials($key, $credentials)
     {
-        $ttl = Carbon::now()->addSeconds($credentials->expires_in)->subMinute();
+        $ttlSeconds = (int) $credentials->expires_in;
+        $ttl = Carbon::now()->addSeconds($ttlSeconds)->subMinute();
 
         $this->core->cache()->put($key, $credentials->access_token, $ttl);
     }