tkinter menubar disappears when matplotlib figure opens

Question

I created a tkinter frame with menus. The frame contains a button that generates a matplotlib figure window. When the figure window opens, all of the menus for the frame disappear (at least on a mac).

A minimal code example is shown below.

Any ideas would be much appreciated. Thanks!

#!/usr/bin/python

import matplotlib.pyplot as plt

import sys
if sys.version_info[0] < 3:
    import Tkinter as tk
else:
    import tkinter as tk


class a_window_with_a_menubar:
    def __init__(self):
        self.root = tk.Tk()                

        self.new_fig_button = tk.Button(master = self.root, text="Make figure", command = self.make_figure)
        self.new_fig_button.grid(row = 0, column = 0, sticky = tk.W)


    def make_figure(self):
        self.fig1 = plt.figure(facecolor = 'white')
        self.ax1 = self.fig1.add_subplot(111)  
        self.ax1.cla()

        plt.show()


win = a_window_with_a_menubar()
tk.mainloop()

Note: the menus disappear whether I use the default tkinter menus or create my own.