How to prevent background scrolling in canvas?

I am using ttk.Scrollbar to scroll elements inside a Tkinter.Canvas. Unfortunately a background image of this canvas will also scroll. How can I prevent this?

Here is an example of what I use:

import Tkinter as tk
from ttk import *

# first canvas with scrollbar
root = tk.Tk()
canv1 = tk.Canvas(root, width=200, height=200, bg='green')
sbar = Scrollbar(root, orient="vertical")
sbar.config(command=canv1.yview)
sbar.pack(side="right", fill="y")      
canv1.config(yscrollcommand=sbar.set)
canv1.pack(side="right", fill="y")

# background of dirst canvas
photo_content2 = tk.PhotoImage(file = './sample_image.gif')
canv1.create_image(115,300, image=photo_content2)

# scrollable second canvas insode first
canv2 = tk.Canvas(canv1, width=50, height=30, bg='red')
canv2.pack()
canv1.create_window(20,20, window=canv2)
canv1.config(scrollregion=(0,0,300,1000))

root.mainloop()