diff --git a/src/rt/rustrt.def.in b/src/rt/rustrt.def.in
index 8b5d9c8fc8e..029e13e2ca0 100644
--- a/src/rt/rustrt.def.in
+++ b/src/rt/rustrt.def.in
@@ -125,6 +125,7 @@ rust_uv_helper_uv_write_t_size
 rust_uv_helper_uv_err_t_size
 rust_uv_helper_sockaddr_in_size
 rust_uv_helper_uv_async_t_size
+rust_uv_helper_uv_timer_t_size
 rust_uv_get_stream_handle_from_connect_req
 rust_uv_get_stream_handle_from_write_req
 rust_uv_get_loop_for_uv_handle