diff --git a/CHANGELOG.md b/CHANGELOG.md
index 633b94d..959cdef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,18 @@ All notable changes to WooCommerce Tier and Package Prices will be documented in
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.1.5] - 2025-12-21
+
+### Fixed
+- **CRITICAL:** Plugin activation error in v1.1.3 and v1.1.4 caused by `add_cart_quantity_css()` method
+- Fatal error when WooCommerce cart object not available during plugin initialization
+- Frontend errors on admin pages and during activation
+
+### Technical
+- Added `function_exists('WC')` check before accessing WooCommerce functions
+- Added `is_admin()` check to prevent CSS injection on admin pages
+- Enhanced error prevention in `add_cart_quantity_css()` method
+
 ## [1.1.4] - 2025-12-21
 
 ### Added
diff --git a/composer.json b/composer.json
index 34a4dbf..577130e 100644
--- a/composer.json
+++ b/composer.json
@@ -1,7 +1,7 @@
 {
     "name": "magdev/wc-tier-package-prices",
     "description": "WooCommerce plugin for tier pricing and package prices with Twig templates",
-    "version": "1.1.4",
+    "version": "1.1.5",
     "type": "wordpress-plugin",
     "license": "GPL-2.0-or-later",
     "authors": [
diff --git a/includes/class-wc-tpp-cart.php b/includes/class-wc-tpp-cart.php
index f2a9d2e..d334f7e 100644
--- a/includes/class-wc-tpp-cart.php
+++ b/includes/class-wc-tpp-cart.php
@@ -188,7 +188,7 @@ class WC_TPP_Cart {
 
     public function add_cart_quantity_css() {
         // Get all cart items and check which products have restrictions
-        if (!WC()->cart) {
+        if (!function_exists('WC') || !WC()->cart || is_admin()) {
             return;
         }
 
diff --git a/languages/wc-tier-package-prices-de_CH_informal.mo b/languages/wc-tier-package-prices-de_CH_informal.mo
index c4057a1..e3767a8 100644
Binary files a/languages/wc-tier-package-prices-de_CH_informal.mo and b/languages/wc-tier-package-prices-de_CH_informal.mo differ
diff --git a/languages/wc-tier-package-prices-de_CH_informal.po b/languages/wc-tier-package-prices-de_CH_informal.po
index 0bfbe8c..8fb6239 100644
--- a/languages/wc-tier-package-prices-de_CH_informal.po
+++ b/languages/wc-tier-package-prices-de_CH_informal.po
@@ -3,7 +3,7 @@
 # This file is distributed under the GPL v2 or later.
 msgid ""
 msgstr ""
-"Project-Id-Version: WooCommerce Tier and Package Prices 1.1.4\n"
+"Project-Id-Version: WooCommerce Tier and Package Prices 1.1.5\n"
 "Report-Msgid-Bugs-To: https://src.bundespruefstelle.ch/wc-tier-package-prices\n"
 "POT-Creation-Date: 2025-12-21 00:00+0000\n"
 "PO-Revision-Date: 2025-12-21 00:00+0000\n"
diff --git a/languages/wc-tier-package-prices-de_DE.mo b/languages/wc-tier-package-prices-de_DE.mo
index 519e6d2..c6eb948 100644
Binary files a/languages/wc-tier-package-prices-de_DE.mo and b/languages/wc-tier-package-prices-de_DE.mo differ
diff --git a/languages/wc-tier-package-prices-de_DE.po b/languages/wc-tier-package-prices-de_DE.po
index df9e7c3..5e1fd76 100644
--- a/languages/wc-tier-package-prices-de_DE.po
+++ b/languages/wc-tier-package-prices-de_DE.po
@@ -3,7 +3,7 @@
 # This file is distributed under the GPL v2 or later.
 msgid ""
 msgstr ""
-"Project-Id-Version: WooCommerce Tier and Package Prices 1.1.4\n"
+"Project-Id-Version: WooCommerce Tier and Package Prices 1.1.5\n"
 "Report-Msgid-Bugs-To: https://src.bundespruefstelle.ch/wc-tier-package-prices\n"
 "POT-Creation-Date: 2025-12-21 00:00+0000\n"
 "PO-Revision-Date: 2025-12-21 00:00+0000\n"
diff --git a/languages/wc-tier-package-prices-en_US.mo b/languages/wc-tier-package-prices-en_US.mo
index 053659f..1688963 100644
Binary files a/languages/wc-tier-package-prices-en_US.mo and b/languages/wc-tier-package-prices-en_US.mo differ
diff --git a/languages/wc-tier-package-prices-en_US.po b/languages/wc-tier-package-prices-en_US.po
index f7b3053..9c21c85 100644
--- a/languages/wc-tier-package-prices-en_US.po
+++ b/languages/wc-tier-package-prices-en_US.po
@@ -3,7 +3,7 @@
 # This file is distributed under the GPL v2 or later.
 msgid ""
 msgstr ""
-"Project-Id-Version: WooCommerce Tier and Package Prices 1.1.4\n"
+"Project-Id-Version: WooCommerce Tier and Package Prices 1.1.5\n"
 "Report-Msgid-Bugs-To: https://src.bundespruefstelle.ch/wc-tier-package-prices\n"
 "POT-Creation-Date: 2025-12-21 00:00+0000\n"
 "PO-Revision-Date: 2025-12-21 00:00+0000\n"
diff --git a/languages/wc-tier-package-prices.pot b/languages/wc-tier-package-prices.pot
index e50faf0..a44a67a 100644
--- a/languages/wc-tier-package-prices.pot
+++ b/languages/wc-tier-package-prices.pot
@@ -2,7 +2,7 @@
 # This file is distributed under the GPL v2 or later.
 msgid ""
 msgstr ""
-"Project-Id-Version: WooCommerce Tier and Package Prices 1.1.4\n"
+"Project-Id-Version: WooCommerce Tier and Package Prices 1.1.5\n"
 "Report-Msgid-Bugs-To: https://src.bundespruefstelle.ch/wc-tier-package-prices\n"
 "POT-Creation-Date: 2025-12-21 00:00+0000\n"
 "MIME-Version: 1.0\n"
diff --git a/wc-tier-and-package-prices.php b/wc-tier-and-package-prices.php
index e441515..81b8312 100644
--- a/wc-tier-and-package-prices.php
+++ b/wc-tier-and-package-prices.php
@@ -4,7 +4,7 @@
  * Plugin Name: WooCommerce Tier and Package Prices
  * Plugin URI: https://src.bundespruefstelle.ch/wc-tier-package-prices
  * Description: Add tier pricing and package prices to WooCommerce products with configurable quantities at fixed prices
- * Version: 1.1.4
+ * Version: 1.1.5
  * Author: Marco Graetsch
  * Author URI: https://src.bundespruefstelle.ch/magdev
  * Text Domain: wc-tier-package-prices
@@ -22,7 +22,7 @@ if (!defined('ABSPATH')) {
 }
 
 // Define plugin constants
-define('WC_TPP_VERSION', '1.1.4');
+define('WC_TPP_VERSION', '1.1.5');
 define('WC_TPP_PLUGIN_DIR', plugin_dir_path(__FILE__));
 define('WC_TPP_PLUGIN_URL', plugin_dir_url(__FILE__));
 define('WC_TPP_PLUGIN_BASENAME', plugin_basename(__FILE__));