diff --git a/src/matrix-http-api.c b/src/matrix-http-api.c
index 39bb2ce..b2e4379 100644
--- a/src/matrix-http-api.c
+++ b/src/matrix-http-api.c
@@ -1688,6 +1688,48 @@ i_forget_room(MatrixAPI *api,
     g_free(path);
 }
 
+static void
+i_invite_user_3rdparty(MatrixAPI *api,
+                       MatrixAPICallback callback,
+                       gpointer user_data,
+                       const gchar *room_id,
+                       const gchar *address,
+                       const gchar *medium,
+                       const gchar *id_server,
+                       GError **error)
+{
+    gchar *encoded_room_id, *path;
+    JsonBuilder *builder;
+    JsonNode *body;
+
+    encoded_room_id = soup_uri_encode(room_id, NULL);
+    path = g_strdup_printf("rooms/%s/invite", encoded_room_id);
+    g_free(encoded_room_id);
+
+    builder = json_builder_new();
+    json_builder_begin_object(builder);
+
+    json_builder_set_member_name(builder, "id_server");
+    json_builder_add_string_value(builder, id_server);
+
+    json_builder_set_member_name(builder, "medium");
+    json_builder_add_string_value(builder, medium);
+
+    json_builder_set_member_name(builder, "address");
+    json_builder_add_string_value(builder, address);
+
+    json_builder_end_object(builder);
+    body = json_builder_get_root(builder);
+    g_object_unref(builder);
+
+    _send(MATRIX_HTTP_API(api),
+          callback, user_data,
+          CALL_API,
+          "POST", path, NULL, NULL, body, NULL,
+          FALSE, error);
+    g_free(path);
+}
+
 static void
 matrix_http_api_matrix_api_init(MatrixAPIInterface *iface)
 {
@@ -1731,7 +1773,7 @@ matrix_http_api_matrix_api_init(MatrixAPIInterface *iface)
     /* Room membership */
     iface->ban_user = i_ban_user;
     iface->forget_room = i_forget_room;
-    iface->invite_user_3rdparty = NULL;
+    iface->invite_user_3rdparty = i_invite_user_3rdparty;
     iface->invite_user = NULL;
     iface->join_room = i_join_room;
     iface->leave_room = i_leave_room;