diff --git a/plugins/files/gitg-files-tree-store.vala b/plugins/files/gitg-files-tree-store.vala
index d2b67e5e..fd81f9cf 100644
--- a/plugins/files/gitg-files-tree-store.vala
+++ b/plugins/files/gitg-files-tree-store.vala
@@ -121,7 +121,7 @@ public class TreeStore : Gtk.TreeStore
 		{
 			d_tree.walk((root, entry) => {
 				var attr = entry.get_file_mode();
-				var isdir = Posix.S_ISDIR(attr);
+				var isdir = attr == Ggit.FileMode.TREE;
 
 				Gtk.TreeIter? parent = null;