diff --git a/commerce_coupon.module b/commerce_coupon.module
index 5adb5f8..eb2cc8a 100644
--- a/commerce_coupon.module
+++ b/commerce_coupon.module
@@ -213,6 +213,7 @@ function commerce_coupon_code_is_valid($code, $order) {
 
   // if no such coupon found, the $code is invalid
   if (!is_object($coupon)) {
+    $commerce_coupon_validation_error_message = t('Coupon code is invalid.');
     return FALSE;
   }