diff --git a/themes/intotheeast/templates/gpx-manager.html.twig b/themes/intotheeast/templates/gpx-manager.html.twig
index 5d8994d..3ed28d5 100644
--- a/themes/intotheeast/templates/gpx-manager.html.twig
+++ b/themes/intotheeast/templates/gpx-manager.html.twig
@@ -54,6 +54,14 @@ function formatSize(bytes) {
     return (bytes / 1024).toFixed(0) + ' KB';
 }
 
+function slugifyFilename(filename) {
+    const lastDot = filename.lastIndexOf('.');
+    const name = lastDot > 0 ? filename.slice(0, lastDot) : filename;
+    const ext  = lastDot > 0 ? filename.slice(lastDot).toLowerCase() : '';
+    const slug = name.toLowerCase().replace(/[^a-z0-9]+/g, '-').replace(/-+/g, '-').replace(/^-|-$/g, '');
+    return slug + ext;
+}
+
 function formatDate(iso) {
     return new Date(iso).toLocaleDateString(undefined, { year: 'numeric', month: 'short', day: 'numeric' });
 }
@@ -131,7 +139,7 @@ function initUpload(formEl) {
         btn.disabled = true;
 
         const fd = new FormData();
-        fd.append('file', file);
+        fd.append('file', new File([file], slugifyFilename(file.name), { type: file.type }));
 
         const res = await apiFetch(`${API}/pages${route}/media`, { method: 'POST', body: fd });
         btn.disabled = false;