diff --git a/src/exchange/taler-exchange-httpd_db.c b/src/exchange/taler-exchange-httpd_db.c
index 2cd879cf3..6b27a22a6 100644
--- a/src/exchange/taler-exchange-httpd_db.c
+++ b/src/exchange/taler-exchange-httpd_db.c
@@ -930,7 +930,7 @@ refresh_check_melt (struct MHD_Connection *connection,
   if (TALER_amount_cmp (&coin_value,
                         &spent) < 0)
   {
-    GNUNET_assert (GNUNET_OK ==
+    GNUNET_assert (GNUNET_SYSERR !=
                    TALER_amount_subtract (&coin_residual,
                                           &spent,
                                           &coin_details->melt_amount_with_fee));