diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 5c2a3fd9..d1057e85 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -17,6 +17,8 @@ jobs:
         php-version:
           - 8.2
           - 8.3
+          - 8.4
+          - 8.5
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -92,6 +94,8 @@ jobs:
             typo3-version: '^13.4'
           - php-version: '8.4'
             typo3-version: '^13.4'
+          - php-version: '8.5'
+            typo3-version: '^13.4'
     steps:
       - uses: actions/checkout@v4
 
@@ -131,6 +135,9 @@ jobs:
       - name: Run Unit Tests PHP8.4
         run: nix-shell --arg phpVersion \"php84\" --pure --run project-test-unit
 
+#      - name: Run Unit Tests PHP8.5
+#        run: nix-shell --arg phpVersion \"php85\" --pure --run project-test-unit
+
       - name: Run Functional Tests PHP8.2
         run: nix-shell --arg phpVersion \"php82\" --pure --run project-test-functional
 
@@ -140,3 +147,6 @@ jobs:
       - name: Run Functional Tests PHP8.4
         run: nix-shell --arg phpVersion \"php84\" --pure --run project-test-functional
 
+#      - name: Run Functional Tests PHP8.5
+#        run: nix-shell --arg phpVersion \"php85\" --pure --run project-test-functional
+
diff --git a/Classes/Service/TaxClassService.php b/Classes/Service/TaxClassService.php
index 65ff9000..a1615a45 100644
--- a/Classes/Service/TaxClassService.php
+++ b/Classes/Service/TaxClassService.php
@@ -39,7 +39,8 @@ public function getTaxClasses(?string $countryCode = null): array
         $taxClassSettings = $this->settings['taxClasses'];
 
         if (
-            array_key_exists($countryCode, $taxClassSettings)
+            is_null($countryCode) === false
+            && array_key_exists($countryCode, $taxClassSettings)
             && is_array($taxClassSettings[$countryCode])
         ) {
             $taxClassSettings = $taxClassSettings[$countryCode];
diff --git a/Documentation/guides.xml b/Documentation/guides.xml
index 6eaa3665..11cd7650 100644
--- a/Documentation/guides.xml
+++ b/Documentation/guides.xml
@@ -11,8 +11,8 @@
                interlink-shortcode="extcode/cart"
     />
     <project title="Cart"
-             release="11.5.0"
-             version="11.5"
+             release="11.6.0"
+             version="11.6"
              copyright="2018 - 2025"
     />
     <inventory id="t3tsref" url="https://docs.typo3.org/typo3cms/TyposcriptReference/"/>
diff --git a/README.md b/README.md
index e381537a..aee99e82 100644
--- a/README.md
+++ b/README.md
@@ -50,8 +50,8 @@ Sometimes minor versions also result in minor adjustments to own templates or co
 
 | Cart   | TYPO3      | PHP       | Support/Development                  |
 |--------|------------|-----------|--------------------------------------|
-| 11.x.x | 13.4       | 8.2 - 8.4 | Features, Bugfixes, Security Updates |
-| 10.x.x | 12.4       | 8.1 - 8.4 | Bugfixes, Security Updates           |
+| 11.x.x | 13.4       | 8.2 - 8.5 | Features, Bugfixes, Security Updates |
+| 10.x.x | 12.4       | 8.1 - 8.5 | Bugfixes, Security Updates           |
 | 9.x.x  | 12.4       | 8.1 - 8.4 | Security Updates                     |
 | 8.x.x  | 10.4, 11.5 | 7.2+      | Security Updates                     |
 | 7.x.x  | 10.4       | 7.2 - 7.4 |                                      |
diff --git a/Tests/Unit/Validation/Validator/EmptyValidatorTest.php b/Tests/Unit/Validation/Validator/EmptyValidatorTest.php
index f86974e2..5ced1c1a 100644
--- a/Tests/Unit/Validation/Validator/EmptyValidatorTest.php
+++ b/Tests/Unit/Validation/Validator/EmptyValidatorTest.php
@@ -99,7 +99,7 @@ public function emptyValidatorWorksForCountableObjects(): void
     public function emptyValidatorWorksForEmptyCountableObjects(): void
     {
         $countableObject = new \SplObjectStorage();
-        $countableObject->attach(new \stdClass());
+        $countableObject->offsetSet(new \stdClass());
         self::assertTrue($this->validator->validate($countableObject)->hasErrors());
     }
 }
diff --git a/composer.json b/composer.json
index 2480ea8d..f55eada1 100644
--- a/composer.json
+++ b/composer.json
@@ -48,7 +48,7 @@
         }
     },
     "require": {
-        "php": "~8.2.0 || ~8.3.0 || ~8.4.0",
+        "php": "~8.2.0 || ~8.3.0 || ~8.4.0 || ~8.5.0",
         "ext-json": "*",
         "ext-openssl": "*",
         "typo3/cms-core": "^13.4",
diff --git a/ext_emconf.php b/ext_emconf.php
index 90f83e22..ae5f0661 100644
--- a/ext_emconf.php
+++ b/ext_emconf.php
@@ -4,14 +4,14 @@
     'title' => 'Cart',
     'description' => 'Shopping Cart(s) for TYPO3',
     'category' => 'plugin',
-    'version' => '11.5.0',
+    'version' => '11.6.0',
     'state' => 'stable',
     'author' => 'Daniel Gohlke',
     'author_email' => 'ext@extco.de',
     'author_company' => 'extco.de UG (haftungsbeschränkt)',
     'constraints' => [
         'depends' => [
-            'php' => '8.2.0-8.4.99',
+            'php' => '8.2.0-8.5.99',
             'typo3' => '13.4.0-13.4.99',
             'extbase' => '13.4.0-13.4.99',
             'fluid' => '13.4.0-13.4.99',
diff --git a/shell.nix b/shell.nix
index c0a30c3b..62da0107 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,10 +1,11 @@
 {
   pkgs ? import <nixpkgs> { }
+  ,phpPkgs ? import (fetchTarball "https://github.com/piotrkwiecinski/nixpkgs/archive/1c614d75004b9eb1ecda6ddeb959c4f544403de5.tar.gz") {}
   ,phpVersion ? "php82"
 }:
 
 let
-  php = pkgs.${phpVersion}.buildEnv {
+  php = phpPkgs.${phpVersion}.buildEnv {
     extensions = { enabled, all }: enabled ++ (with all; [
       xdebug
     ]);
@@ -14,7 +15,7 @@ let
       memory_limit = 4G
     '';
   };
-  inherit(pkgs."${phpVersion}Packages") composer;
+  inherit(phpPkgs."${phpVersion}Packages") composer;
 
   projectInstall = pkgs.writeShellApplication {
     name = "project-install";