diff --git a/src/app/file_list.rs b/src/app/file_list.rs
index 13ed037..031e180 100644
--- a/src/app/file_list.rs
+++ b/src/app/file_list.rs
@@ -250,7 +250,8 @@ impl App {
                 // Measured once, from the panel rather than from the scrolled
                 // content: reading `available_width()` inside a row makes the
                 // content's width depend on the content's width.
-                let row_width = ui.available_width();
+                // Cap the width to prevent the panel from expanding infinitely.
+                let row_width = ui.available_width().min(580.0);
                 let nested = rows.iter().any(|r| r.depth > 0);
 
                 egui::ScrollArea::vertical()