diff --git a/includes/class-wc-ajax.php b/includes/class-wc-ajax.php
index 1dade2307b2..54a22f95e97 100644
--- a/includes/class-wc-ajax.php
+++ b/includes/class-wc-ajax.php
@@ -908,7 +908,7 @@ class WC_AJAX {
 				$validation_error = apply_filters( 'woocommerce_ajax_add_order_item_validation', $validation_error, $product, $order, $qty );
 
 				if ( $validation_error->get_error_code() ) {
-					throw new Exception( '<strong>' . __( 'Error:', 'woocommerce' ) . '</strong> ' . $validation_error->get_error_message() );
+					throw new Exception( sprintf( __( 'Error: %s', 'woocommerce' ), $validation_error->get_error_message() ) );
 				}
 				$item_id                 = $order->add_product( $product, $qty );
 				$item                    = apply_filters( 'woocommerce_ajax_order_item', $order->get_item( $item_id ), $item_id, $order, $product );