Band calculation error with rasterio in Python

I am new to GIS in Python and want to perform a simple band calculation from Sentinel-2 imagery using rasterio and numpy – specifically, I want to divide Sentinel Band 11 (SWIR) by Band 8 (NIR) to map snow/ice.

I have written the following code:

    import numpy as np
    import rasterio as rio

    band11 = rio.open('filename_b11.jp2', driver = 'JP2OpenJPEG') #swir
    band8 = rio.open('filename_b8.jp2', driver = 'JP2OpenJPEG') #nir

    # convert to float
    swir = band11.read(1).astype('float64')
    nir = band8.read(1).astype('float64')

    # divide swir by nir
    band_calc = (swir / nir)

This produces the following error:

    ValueError: operands could not be broadcast together with shapes (5490,5490) (10980,10980)

How do I handle this error (i.e. where the shapes of the two bands are not matching) to perform the band calculation, and similar calculations such as the NDSI?