diff --git a/CHANGELOG.md b/CHANGELOG.md
index cac35d98d..9874425b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- relay: fix crash after `/upgrade` when relay clients are connected
 - api: allow to add empty buffer with function infolist_new_var_buffer
 - core: fix detection of dl library ([#2218](https://github.com/weechat/weechat/issues/2218))
 - logger: fix path displayed when the logs directory can not be created
diff --git a/src/plugins/relay/relay-client.c b/src/plugins/relay/relay-client.c
index e4975a2f6..53562451c 100644
--- a/src/plugins/relay/relay-client.c
+++ b/src/plugins/relay/relay-client.c
@@ -1696,6 +1696,11 @@ relay_client_new_with_infolist (struct t_infolist *infolist)
                 new_client->partial_ws_frame_size = ws_frame_size;
             }
         }
+        else
+        {
+            new_client->partial_ws_frame = NULL;
+            new_client->partial_ws_frame_size = 0;
+        }
         str = weechat_infolist_string (infolist, "partial_message");
         new_client->partial_message = (str) ? strdup (str) : NULL;