diff --git a/src/server/upload.cxx b/src/server/upload.cxx
index 8eaa68d..57c6918 100644
--- a/src/server/upload.cxx
+++ b/src/server/upload.cxx
@@ -93,7 +93,7 @@ void Server::upload(const std::shared_ptr<restbed::Session> &s) {
         auto node = get_node(user, node_id);
         if (!node) return s->close(400, "Invalid node");
         if (!node->file) return s->close(400, "Can't upload to a directory");
-        std::size_t to_read = req->get_header("Content-Length", 0);
+        auto to_read = req->get_header<std::size_t>("Content-Length", 0);
         auto path = user->user_dir / std::to_string(node->id);
         if (node->preview) {
             node->preview = false;