diff --git a/composer.json b/composer.json
index ac49869..2bb6211 100644
--- a/composer.json
+++ b/composer.json
@@ -28,7 +28,7 @@
         "netglue/laminas-mail-utils": "^0",
         "netglue/psr-container-postmark": "^1.6.0",
         "psr/cache": "^1.0 || ^2.0.0 || ^3.0.0",
-        "wildbit/postmark-php": "^4.0"
+        "wildbit/postmark-php": "^4.0 || ^5.0"
     },
     "autoload": {
         "psr-4": {