diff --git a/CHANGELOG.md b/CHANGELOG.md
index b3495fd..eef10e3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,9 @@ each change under the current top section as you work.
 
 ## [1.5.5]
 
+### Changed
+- **Payments now run on the current Stripe library.** The plugin had fallen four major versions behind Stripe's PHP SDK, which also meant it was asking Stripe to behave like an older version of its API. Taking a card payment and handling a webhook work exactly as before — the same charge is raised, the same events are honoured, and a forged webhook is still rejected — but the plugin now speaks Stripe's current API version, so later payment work does not have to clear this upgrade first. Nothing to do on your side.
+
 ## [1.5.4]
 
 ### Fixed
diff --git a/composer.json b/composer.json
index fc0735b..8a2fbc2 100644
--- a/composer.json
+++ b/composer.json
@@ -5,7 +5,7 @@
     "license": "GPL-2.0-or-later",
     "require": {
         "php": ">=8.1",
-        "stripe/stripe-php": "^17.0"
+        "stripe/stripe-php": "^21.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^10.5",
diff --git a/composer.lock b/composer.lock
index 444fa8c..132f9e2 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,32 +4,32 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "24094d05e029ee5534769a89f1dbad12",
+    "content-hash": "015f4bbb03f15362596d3a14aeca1582",
     "packages": [
         {
             "name": "stripe/stripe-php",
-            "version": "v17.6.0",
+            "version": "v21.2.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/stripe/stripe-php.git",
-                "reference": "a6219df5df1324a0d3f1da25fb5e4b8a3307ea16"
+                "reference": "da798f6224c5ff6f89d8d78025044f418ee27db8"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/stripe/stripe-php/zipball/a6219df5df1324a0d3f1da25fb5e4b8a3307ea16",
-                "reference": "a6219df5df1324a0d3f1da25fb5e4b8a3307ea16",
+                "url": "https://api.github.com/repos/stripe/stripe-php/zipball/da798f6224c5ff6f89d8d78025044f418ee27db8",
+                "reference": "da798f6224c5ff6f89d8d78025044f418ee27db8",
                 "shasum": ""
             },
             "require": {
                 "ext-curl": "*",
                 "ext-json": "*",
                 "ext-mbstring": "*",
-                "php": ">=5.6.0"
+                "php": ">=7.2.0"
             },
             "require-dev": {
-                "friendsofphp/php-cs-fixer": "3.72.0",
+                "friendsofphp/php-cs-fixer": "3.94.0",
                 "phpstan/phpstan": "^1.2",
-                "phpunit/phpunit": "^5.7 || ^9.0"
+                "phpunit/phpunit": "^8.0 || ^9.0"
             },
             "type": "library",
             "extra": {
@@ -38,6 +38,9 @@
                 }
             },
             "autoload": {
+                "files": [
+                    "lib/version_check.php"
+                ],
                 "psr-4": {
                     "Stripe\\": "lib/"
                 }
@@ -61,9 +64,9 @@
             ],
             "support": {
                 "issues": "https://github.com/stripe/stripe-php/issues",
-                "source": "https://github.com/stripe/stripe-php/tree/v17.6.0"
+                "source": "https://github.com/stripe/stripe-php/tree/v21.2.1"
             },
-            "time": "2025-08-27T19:32:42+00:00"
+            "time": "2026-08-20T21:06:13+00:00"
         }
     ],
     "packages-dev": [