diff --git a/panda/src/downloader/config_downloader.h b/panda/src/downloader/config_downloader.h
index 5fffc29692..fec0bef24a 100644
--- a/panda/src/downloader/config_downloader.h
+++ b/panda/src/downloader/config_downloader.h
@@ -47,7 +47,7 @@ extern ConfigVariableInt http_skip_body_size;
 extern ConfigVariableDouble http_idle_timeout;
 extern ConfigVariableInt http_max_connect_count;
 
-extern ConfigVariableInt tcp_header_size;
+extern EXPCL_PANDAEXPRESS ConfigVariableInt tcp_header_size;
 
 extern EXPCL_PANDAEXPRESS void init_libdownloader();