diff --git a/CHANGELOG.md b/CHANGELOG.md
index a0cd709..03acdf7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,12 @@
 # Changelog
 All notable changes to the Tax Switch for Woocommerce plugin will be documented in this file.
 
+## [1.1.9] - 2024-11-04
+### Added
+- Extra check for filtering backend and frontend AJAX requests (which adds compatibility for [PDF Invoices & Packing Slips for WooCommerce](https://wordpress.org/plugins/woocommerce-pdf-invoices-packing-slips/)).
+### Updated
+- Fixed a bug where the admin request checks failed when Wordpress is installed in a subdirectory.
+
 ## [1.1.8] - 2024-10-25
 ### Added
 - Compatibility for YITH WooCommerce Product Add-ons & Extra Options Premium
diff --git a/README.txt b/README.txt
index 10a13ed..45e78cd 100644
--- a/README.txt
+++ b/README.txt
@@ -3,7 +3,7 @@ Contributors: wijnbergdevelopments
 Tags: woocommerce, tax, vat
 Requires at least: 5.0
 Tested up to: 6.6
-Stable tag: 1.1.8
+Stable tag: 1.1.9
 Requires PHP: 7.2
 License: GPL-2.0+
 License URI: http://www.gnu.org/licenses/gpl-2.0.txt
@@ -77,6 +77,9 @@ You can also use this shortcode in your theme files with the do_shortcode() func
 Some WooCommerce Blocks are not fully compatible with this plugin as they do not use standard WooCommerce filters for price display. This is a known limitation of WooCommerce Blocks and not specific to this plugin. You can fix this by using WooCommerce shortcodes instead of the WooCommerce Blocks.
 
 == Changelog ==
+= 1.1.9 =
+* Added extra check for filtering backend and frontend AJAX requests (which adds compatibility for [PDF Invoices & Packing Slips for WooCommerce](https://wordpress.org/plugins/woocommerce-pdf-invoices-packing-slips/))
+* Fixed a bug where the admin request checks failed when Wordpress is installed in a subdirectory
 
 = 1.1.8 =
 * Added compatibility for YITH WooCommerce Product Add-ons & Extra Options Premium
diff --git a/block/src/block.json b/block/src/block.json
index 3813e83..346ece6 100644
--- a/block/src/block.json
+++ b/block/src/block.json
@@ -2,7 +2,7 @@
 	"$schema": "https://schemas.wp.org/trunk/block.json",
 	"apiVersion": 3,
 	"name": "wdevs/tax-switch",
-	"version": "1.1.8",
+	"version": "1.1.9",
 	"title": "Tax Switch for WooCommerce",
 	"category": "woocommerce",
 	"icon": "money-alt",
diff --git a/block/src/compatibility/ProductAddOns.js b/block/src/compatibility/ProductAddOns.js
index a99ec27..44dbf2b 100644
--- a/block/src/compatibility/ProductAddOns.js
+++ b/block/src/compatibility/ProductAddOns.js
@@ -88,8 +88,8 @@ class ProductAddOns {
 							}
 						}
 					}
-					vm.handlePriceUpdate();
 				}
+				vm.handlePriceUpdate();
 			}
 		}, 10 );
 	}
@@ -132,6 +132,7 @@ class ProductAddOns {
 
 	handlePriceUpdate() {
 		const elements = {
+			productPrice: jQuery( '#wapo-total-product-price' ),
 			options: jQuery( '#wapo-total-options-price' ),
 			order: jQuery( '#wapo-total-order-price' ),
 		};
diff --git a/includes/class-wdevs-tax-switch.php b/includes/class-wdevs-tax-switch.php
index 37fe6b6..d590fda 100644
--- a/includes/class-wdevs-tax-switch.php
+++ b/includes/class-wdevs-tax-switch.php
@@ -366,9 +366,16 @@ private function is_admin_request() {
 		/**
 		 * Get current URL.
 		 *
-		 * @link https://wordpress.stackexchange.com/a/126534
+		 * @link https://wordpress.stackexchange.com/a/237498/178511
 		 */
-		$current_url = home_url( add_query_arg( null, null ) );
+		$parts = parse_url(home_url());
+		$current_url   = $parts['scheme'] . '://' . $parts['host'];
+
+		if (array_key_exists('port', $parts)) {
+			$current_url .= ':' . $parts['port'];
+		}
+
+		$current_url .= add_query_arg([]);
 
 		/**
 		 * Get admin URL and referrer.
@@ -389,7 +396,7 @@ private function is_admin_request() {
 			if ( 0 === strpos( $referrer, $admin_url ) ) {
 				return true;
 			} else {
-				return ! $this->is_doing_ajax();
+				return ! $this->is_frontend_ajax_request();
 			}
 		} else {
 			return false;
@@ -411,4 +418,28 @@ private function is_doing_ajax() {
 		}
 	}
 
+	/**
+	 * @return bool
+	 * @since 1.1.9
+	 */
+	private function is_frontend_ajax_request() {
+
+		$script_filename = isset( $_SERVER['SCRIPT_FILENAME'] ) ? $_SERVER['SCRIPT_FILENAME'] : '';
+
+		if ( $this->is_doing_ajax() ) {
+			$referrer_raw = wp_get_raw_referer();
+			if ( $referrer_raw === false ) {
+				return false;
+			}
+
+			//If referer does not contain admin URL and we are using the admin-ajax.php endpoint, this is likely a frontend AJAX request
+			if ( ( ( strpos( $referrer_raw, admin_url() ) === false ) && ( basename( $script_filename ) === 'admin-ajax.php' ) ) ) {
+				return true;
+			}
+		}
+
+		//If no checks triggered, we end up here - not an AJAX request.
+		return false;
+	}
+
 }
diff --git a/package.json b/package.json
index 6ea5b81..e17b684 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "wdevs-tax-switch",
-	"version": "1.1.8",
+	"version": "1.1.9",
 	"description": "Let customers toggle between inclusive and exclusive VAT pricing in your WooCommerce store.",
 	"author": "Wijnberg Developments",
 	"license": "GPL-2.0-or-later",
diff --git a/wdevs-tax-switch.php b/wdevs-tax-switch.php
index d640aaa..360e1a2 100644
--- a/wdevs-tax-switch.php
+++ b/wdevs-tax-switch.php
@@ -16,7 +16,7 @@
  * Plugin Name:          Tax Switch for WooCommerce
  * Plugin URI:           https://wijnberg.dev
  * Description:          Let customers toggle between inclusive and exclusive VAT pricing in your WooCommerce store.
- * Version:              1.1.8
+ * Version:              1.1.9
  * Author:               Wijnberg Developments
  * Author URI:           https://wijnberg.dev/
  * License:              GPL-2.0+
@@ -41,7 +41,7 @@
  * Start at version 1.0.0 and use SemVer - https://semver.org
  * Rename this for your plugin and update it as you release new versions.
  */
-define( 'WDEVS_TAX_SWITCH_VERSION', '1.1.8' );
+define( 'WDEVS_TAX_SWITCH_VERSION', '1.1.9' );
 
 /**
  * The code that runs during plugin activation.