diff --git a/eopayment/systempayv2.py b/eopayment/systempayv2.py
index 3002010..201cb2c 100644
--- a/eopayment/systempayv2.py
+++ b/eopayment/systempayv2.py
@@ -128,7 +128,7 @@ PARAMETERS = [
     Parameter(VADS_TRANS_DATE, 'n', 4, length=14, needed=True,
               default=isonow),
     Parameter('vads_trans_id', 'n', 3, length=6, needed=True),
-    Parameter('vads_validation_mode', 'n', 5, max_length=1, choices=('', 0, 1),
+    Parameter('vads_validation_mode', 'n', 5, max_length=1, choices=('', '0', '1'),
               default=''),
     Parameter('vads_version', 'an', 1, default='V2', needed=True,
               choices=('V2',)),