diff --git a/oceano.py b/oceano.py
index 0dffaec5761e5ec5f4657a241b1be97ebb854f96..866c3c1f68e8fb1af1256d932f5b9686de20e960 100644
--- a/oceano.py
+++ b/oceano.py
@@ -36,7 +36,8 @@ if args.debug:
 if len(sys.argv) == 1:
     # define GUI layout
     layout = ([[sg.Text('File(s) to read and convert')],
-               [sg.Input(size=(40, 1)), sg.FileBrowse()],
+               [sg.Input(size=(40, .8)), sg.FileBrowse(
+                   file_types=(("cnv files", "*.cnv"),))],
                [sg.Checkbox('PRES'), sg.Checkbox('TEMP'), sg.Checkbox('PSAL')],
                [sg.CloseButton('Run'), sg.CloseButton('Cancel')]])