Tkinter checkbutton - text won't show up

When I try to use a checkbutton it works fine but the text won't appear. I can't understand why. Below is my code

from tkinter import *
a = Tk()
var1 = IntVar()
Checkbutton(a, text="checkbutton", variable=var1, fg='blue').grid(row=0,sticky=W)
a.mainloop()

The checkbox appears but the text alongside does not