diff --git a/themes/intotheeast/templates/gpx-manager.html.twig b/themes/intotheeast/templates/gpx-manager.html.twig
index 9bf5135..cddba6c 100644
--- a/themes/intotheeast/templates/gpx-manager.html.twig
+++ b/themes/intotheeast/templates/gpx-manager.html.twig
@@ -138,8 +138,9 @@ function initUpload(formEl) {
         status.className = 'gpx-status';
         btn.disabled = true;
 
+        const slugged = slugifyFilename(file.name);
         const fd = new FormData();
-        fd.append('file', file, slugifyFilename(file.name));
+        fd.append('file', file.slice(0, file.size, file.type), slugged);
 
         const res = await apiFetch(`${API}/pages${route}/media`, { method: 'POST', body: fd });
         btn.disabled = false;