A question about styling a CustomTkinter combobox

Hi all,

Hope it’s ok to ask here, if not please move my post to the right section.

I just started using CustomTkinter and would like to style my widgets.
I’m looking for a way to change/remove this ugly white box around the dropdown of the combobox:

In my custom class (see below) I have used about every property a combobox has, but I can’t get rid of this thick white border. On an (outdated) wiki page it looks like I want it to look:

How can I fix this?

Thanks!

My class:

clr_bgr = '#202020'             # Background
clr_grn = '#009900'             # Green
clr_hvr = '#303030'             # Hover color


class ComboboxCst(ctk.CTkComboBox):

    def __init__(self, master, values, command=None, 
                 width=150, height=20, corner_radius=5,
                 border_width=1, border_color=clr_grn,
                 font=('Arial', 10), text_color=clr_grn, 
                 dropdown_font=('Arial', 10),
                 dropdown_text_color=clr_grn, 
                 fg_color=clr_bgr, dropdown_fg_color=clr_bgr,
                 dropdown_hover_color=clr_hvr, 
                 button_color=clr_hvr, 
                 button_hover_color=clr_hvr,
                 hover=True, justify='left'):

        super().__init__(master, values=values, 
                         command=command, 
                         width=width, height=height,
                         corner_radius=corner_radius, 
                         border_width=border_width,
                         border_color=border_color, 
                         font=font, text_color=text_color,
                         dropdown_font=dropdown_font, 
                         dropdown_text_color=dropdown_text_color,
                         fg_color=fg_color, 
                         dropdown_fg_color=dropdown_fg_color,
                         dropdown_hover_color=dropdown_hover_color,
                         button_color=button_color, 
                         button_hover_color=button_hover_color,
                         hover=hover, justify=justify)