diff --git a/src/exchange/taler-exchange-httpd_age-withdraw.c b/src/exchange/taler-exchange-httpd_age-withdraw.c
index 4257e4c1d..ff37d4cd2 100644
--- a/src/exchange/taler-exchange-httpd_age-withdraw.c
+++ b/src/exchange/taler-exchange-httpd_age-withdraw.c
@@ -306,8 +306,8 @@ TEH_handler_age_withdraw (struct TEH_RequestContext *rc,
     TALER_JSON_spec_amount ("amount",
                             TEH_currency,
                             &awc.commitment.amount_with_fee),
-    GNUNET_JSON_spec_uint8 ("max_age_group",
-                            &awc.commitment.max_age_group),
+    GNUNET_JSON_spec_uint32 ("max_age_group",
+                             &awc.commitment.max_age_group),
     GNUNET_JSON_spec_end ()
   };