diff --git a/core/group_party.go b/core/group_party.go
index 3de416f..b50f530 100644
--- a/core/group_party.go
+++ b/core/group_party.go
@@ -2,6 +2,7 @@ package core
 
 import (
 	"context"
+	"encoding/gob"
 	"encoding/json"
 	"fmt"
 	"net/http"
@@ -63,6 +64,11 @@ type partyDoc struct {
 	id groupID
 }
 
+func init() {
+	gob.Register(partyDoc{})
+	gob.Register(Invitation{})
+}
+
 func (gd *partyDoc) loadMemberFull(tid string) (bson.M, error) {
 	full, err := gd.rh.JSONGet(gd.strid(), "$._members."+tid)
 	if err != nil {