diff --git a/src/exchange/taler-exchange-httpd.c b/src/exchange/taler-exchange-httpd.c
index 68fc9fb72..ffe5c1f5a 100644
--- a/src/exchange/taler-exchange-httpd.c
+++ b/src/exchange/taler-exchange-httpd.c
@@ -1040,6 +1040,7 @@ handle_post_auditors (struct TEH_RequestContext *rc,
                                root);
 }
 
+
 /**
  * Handle GET "/extensions/..." requests.
  *
@@ -1069,7 +1070,10 @@ handle_get_extensions (struct TEH_RequestContext *rc,
   }
 
   if (NULL == ext->http_get_handler)
-    return MHD_HTTP_NOT_IMPLEMENTED;
+    return TALER_MHD_reply_with_error (rc->connection,
+                                       MHD_HTTP_NOT_IMPLEMENTED,
+                                       TALER_EC_EXCHANGE_GENERIC_OPERATION_UNKNOWN,
+                                       "GET /extensions/$EXTENSION not supported");
 
   return ext->http_get_handler (
     rc->connection,
@@ -1108,7 +1112,10 @@ handle_post_extensions (struct TEH_RequestContext *rc,
   }
 
   if (NULL == ext->http_post_handler)
-    return MHD_HTTP_NOT_IMPLEMENTED;
+    return TALER_MHD_reply_with_error (rc->connection,
+                                       MHD_HTTP_NOT_IMPLEMENTED,
+                                       TALER_EC_EXCHANGE_GENERIC_OPERATION_UNKNOWN,
+                                       "POST /extensions/$EXTENSION not supported");
 
   return ext->http_post_handler (
     rc->connection,