diff --git a/src/exchange-lib/exchange_api_handle.c b/src/exchange-lib/exchange_api_handle.c
index 6398bce99..6d3f441c8 100644
--- a/src/exchange-lib/exchange_api_handle.c
+++ b/src/exchange-lib/exchange_api_handle.c
@@ -265,6 +265,7 @@ parse_json_signkey (struct TALER_EXCHANGE_SigningPublicKey *sign_key,
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
+  sign_key->master_sig = sign_key_issue_sig;
   return GNUNET_OK;
 }