diff --git a/api/client-server/v1/sync.yaml b/api/client-server/v1/sync.yaml
index b52908a9..57a15583 100644
--- a/api/client-server/v1/sync.yaml
+++ b/api/client-server/v1/sync.yaml
@@ -131,6 +131,14 @@ paths:
                           "type": "m.presence"
                       }
                   ],
+                  "private_user_data": [
+                    {
+                      "type": "org.example.custom.config",
+                      "content": {
+                        "custom_config_key": "custom_config_value"
+                      }
+                    }
+                  ],
                   "rooms": [
                       {
                           "membership": "join",
@@ -246,10 +254,18 @@ paths:
                               }
                           ],
                           "visibility": "private",
-                          "private_user_data": [{
-                            "type": "m.tag",
-                            "content": {"tags": {"work": {"order": 1}}}
-                          }]
+                          "private_user_data": [
+                            {
+                              "type": "m.tag",
+                              "content": {"tags": {"work": {"order": 1}}}
+                            },
+                            {
+                              "type": "org.example.custom.room.config",
+                              "content": {
+                                "custom_config_key": "custom_config_value"
+                              }
+                            }
+                          ]
                       }
                   ]
               }
diff --git a/api/client-server/v2_alpha/sync.yaml b/api/client-server/v2_alpha/sync.yaml
index 4c1a7601..e180c5ff 100644
--- a/api/client-server/v2_alpha/sync.yaml
+++ b/api/client-server/v2_alpha/sync.yaml
@@ -215,6 +215,16 @@ paths:
                     }
                   ]
                 },
+                "private_user_data": {
+                  "events": [
+                    {
+                      "type": "org.example.custom.config",
+                      "content": {
+                        "custom_config_key": "custom_config_value"
+                      }
+                    }
+                  ]
+                },
                 "rooms": {
                   "joined": {
                     "!726s6s6q:example.com": {
@@ -271,6 +281,12 @@ paths:
                           {
                             "type": "m.tags",
                             "content": {"tags": {"work": {"order": 1}}}
+                          },
+                          {
+                            "type": "org.example.custom.room.config",
+                            "content": {
+                              "custom_config_key": "custom_config_value"
+                            }
                           }
                         ]
                       }