diff --git a/server/templates.go b/server/templates.go
index e46855b1..13e3bfc8 100644
--- a/server/templates.go
+++ b/server/templates.go
@@ -109,7 +109,7 @@ func loadWebConfig(c webConfig) (http.Handler, http.Handler, *templates, error)
 	if err != nil {
 		return nil, nil, nil, fmt.Errorf("read static dir: %v", err)
 	}
-	themeFiles, err := fs.Sub(c.webFS, filepath.Join("themes", c.theme))
+	themeFiles, err := fs.Sub(c.webFS, filepath.ToSlash(filepath.Join("themes", c.theme)))
 	if err != nil {
 		return nil, nil, nil, fmt.Errorf("read themes dir: %v", err)
 	}
@@ -133,7 +133,7 @@ func loadTemplates(c webConfig, templatesDir string) (*templates, error) {
 		if file.IsDir() {
 			continue
 		}
-		filenames = append(filenames, filepath.Join(templatesDir, file.Name()))
+		filenames = append(filenames, filepath.ToSlash(filepath.Join(templatesDir, file.Name())))
 	}
 	if len(filenames) == 0 {
 		return nil, fmt.Errorf("no files in template dir %q", templatesDir)