diff --git a/src/Iban.php b/src/Iban.php
index a6131b474..c7d9e4b71 100644
--- a/src/Iban.php
+++ b/src/Iban.php
@@ -222,7 +222,7 @@ public function setAllowNonSepa($allowNonSepa)
     public function isValid($value)
     {
         if (!is_string($value)) {
-            $this->error(self::INVALID);
+            $this->error(self::FALSEFORMAT);
             return false;
         }