Text bgstipple not working on Mac

Hi!

Following script shows dithered background on Windows and Linux (Tk 8.6) 
but on Mac (both with Tk 8.5 via Python 3.6 and Tk 8.6 via Python 3.7) 
the background remains solid. Is this a known limitation or am I missing 
something?

###############################

import tkinter as tk

root = tk.Tk()
text = tk.Text(root)
text.grid()

text.insert("1.0", """first
second
third
""")

text.tag_configure("bgstip", bgstipple="gray50", background="pink")
text.tag_configure("fgstip", fgstipple="gray50", foreground="blue")
text.tag_add("bgstip", "2.0", "3.2")
text.tag_add("fgstip", "3.0", "3.5")

root.mainloop()

###############################

best regards,
Aivar