diff --git a/modules/ppcp-subscription/src/SubscriptionModule.php b/modules/ppcp-subscription/src/SubscriptionModule.php
index 2b30fae9b..e9e3d1123 100644
--- a/modules/ppcp-subscription/src/SubscriptionModule.php
+++ b/modules/ppcp-subscription/src/SubscriptionModule.php
@@ -233,6 +233,10 @@ class SubscriptionModule implements ModuleInterface {
 			 * @psalm-suppress MissingClosureParamType
 			 */
 			function( string $post_type, $post_or_order_object ) use ( $c ) {
+				if ( ! function_exists( 'wcs_get_subscription' ) ) {
+					return;
+				}
+
 				$order = ( $post_or_order_object instanceof WP_Post )
 					? wc_get_order( $post_or_order_object->ID )
 					: $post_or_order_object;
diff --git a/modules/ppcp-vaulting/src/PaymentTokenChecker.php b/modules/ppcp-vaulting/src/PaymentTokenChecker.php
index cd57e9426..3d7095fb6 100644
--- a/modules/ppcp-vaulting/src/PaymentTokenChecker.php
+++ b/modules/ppcp-vaulting/src/PaymentTokenChecker.php
@@ -215,11 +215,11 @@ class PaymentTokenChecker {
 		$wc_order->update_status( 'failed', $error_message );
 
 		/**
-		 * Function already exist in Subscription plugin
+		 * Function already exist in WC Subscriptions plugin.
 		 *
 		 * @psalm-suppress UndefinedFunction
 		 */
-		$subscriptions = wcs_get_subscriptions_for_order( $wc_order->get_id() );
+		$subscriptions = function_exists( 'wcs_get_subscriptions_for_order' ) ? wcs_get_subscriptions_for_order( $wc_order->get_id() ) : array();
 		foreach ( $subscriptions as $key => $subscription ) {
 			if ( $subscription->get_parent_id() === $wc_order->get_id() ) {
 				try {
diff --git a/modules/ppcp-wc-gateway/src/Gateway/PayPalGateway.php b/modules/ppcp-wc-gateway/src/Gateway/PayPalGateway.php
index c863d1663..2e71ad7a5 100644
--- a/modules/ppcp-wc-gateway/src/Gateway/PayPalGateway.php
+++ b/modules/ppcp-wc-gateway/src/Gateway/PayPalGateway.php
@@ -525,7 +525,7 @@ class PayPalGateway extends \WC_Payment_Gateway {
 				$order = $this->session_handler->order();
 				$this->add_paypal_meta( $wc_order, $order, $this->environment );
 
-				$subscriptions = wcs_get_subscriptions_for_order( $order_id );
+				$subscriptions = function_exists( 'wcs_get_subscriptions_for_order' ) ? wcs_get_subscriptions_for_order( $order_id ) : array();
 				foreach ( $subscriptions as $subscription ) {
 					$subscription->update_meta_data( 'ppcp_subscription', $paypal_subscription_id );
 					$subscription->save();
diff --git a/modules/ppcp-webhooks/src/Handler/BillingSubscriptionCancelled.php b/modules/ppcp-webhooks/src/Handler/BillingSubscriptionCancelled.php
index 0fc79f0d3..6b9df1250 100644
--- a/modules/ppcp-webhooks/src/Handler/BillingSubscriptionCancelled.php
+++ b/modules/ppcp-webhooks/src/Handler/BillingSubscriptionCancelled.php
@@ -81,7 +81,7 @@ class BillingSubscriptionCancelled implements RequestHandler {
 					),
 				),
 			);
-			$subscriptions = wcs_get_subscriptions( $args );
+			$subscriptions = function_exists( 'wcs_get_subscriptions' ) ? wcs_get_subscriptions( $args ) : array();
 			foreach ( $subscriptions as $subscription ) {
 				$subscription->update_status( 'cancelled' );
 			}
diff --git a/modules/ppcp-webhooks/src/Handler/PaymentSaleCompleted.php b/modules/ppcp-webhooks/src/Handler/PaymentSaleCompleted.php
index b606e2bd9..442dabd97 100644
--- a/modules/ppcp-webhooks/src/Handler/PaymentSaleCompleted.php
+++ b/modules/ppcp-webhooks/src/Handler/PaymentSaleCompleted.php
@@ -71,10 +71,13 @@ class PaymentSaleCompleted implements RequestHandler {
 			return $this->failure_response();
 		}
 
+		if ( ! function_exists( 'wcs_get_subscriptions' ) ) {
+			return $this->failure_response( 'WooCommerce Subscriptions plugin is not active.' );
+		}
+
 		$billing_agreement_id = wc_clean( wp_unslash( $request['resource']['billing_agreement_id'] ?? '' ) );
 		if ( ! $billing_agreement_id ) {
-			$message = 'Could not retrieve billing agreement id for subscription.';
-			return $this->failure_response( $message );
+			return $this->failure_response( 'Could not retrieve billing agreement id for subscription.' );
 		}
 
 		$args          = array(