diff --git a/composer.json b/composer.json
index 4ed715c..7f197df 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,7 @@
     },
     "require": {
         "php": "~8.1 || ~8.2",
-        "wildbit/postmark-php": "^2.9||^3.0||^4.0",
+        "wildbit/postmark-php": "^2.9||^3.0||^4.0 || ^5.0",
         "psr/container": "^1.0.0 || ^2.0.0"
     },
     "autoload": {
diff --git a/composer.lock b/composer.lock
index 12f956c..401af17 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "4dcf3d0c1bacbe256465b565aee6369c",
+    "content-hash": "3f32734209b7d572448dd0d2a55a579c",
     "packages": [
         {
             "name": "guzzlehttp/guzzle",
@@ -652,24 +652,25 @@
         },
         {
             "name": "wildbit/postmark-php",
-            "version": "v4.0.5",
+            "version": "v5.0.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/ActiveCampaign/postmark-php.git",
-                "reference": "b71efba061de7cf7e1f853d211b1c5edce4e3c5b"
+                "reference": "c7a437163d8de45938546cabfca7df61988bb0e6"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/ActiveCampaign/postmark-php/zipball/b71efba061de7cf7e1f853d211b1c5edce4e3c5b",
-                "reference": "b71efba061de7cf7e1f853d211b1c5edce4e3c5b",
+                "url": "https://api.github.com/repos/ActiveCampaign/postmark-php/zipball/c7a437163d8de45938546cabfca7df61988bb0e6",
+                "reference": "c7a437163d8de45938546cabfca7df61988bb0e6",
                 "shasum": ""
             },
             "require": {
-                "guzzlehttp/guzzle": "^6.0|^7.0",
-                "php": ">=7.0.0"
+                "guzzlehttp/guzzle": "^7.8",
+                "php": "~8.0 || ~8.1 || ~8.2"
             },
             "require-dev": {
-                "phpunit/phpunit": "^6.0.0"
+                "phpstan/phpstan": "^1.10",
+                "phpunit/phpunit": "^9"
             },
             "type": "library",
             "autoload": {
@@ -684,9 +685,9 @@
             "description": "The officially supported client for Postmark (http://postmarkapp.com)",
             "support": {
                 "issues": "https://github.com/ActiveCampaign/postmark-php/issues",
-                "source": "https://github.com/ActiveCampaign/postmark-php/tree/v4.0.5"
+                "source": "https://github.com/ActiveCampaign/postmark-php/tree/v5.0.1"
             },
-            "time": "2023-02-03T15:00:17+00:00"
+            "time": "2023-11-21T19:19:51+00:00"
         }
     ],
     "packages-dev": [