How to define an integral to not be evaluated

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I'm trying to write the following script:

var('alpha beta x')

num = x**(alpha-1) * (1-x)**(beta-1)
denom = integral(x**(alpha-1) * (1-x)**(beta-1), x)

gammadist = num / denom

diff(gammadist, x)

So it is mich easier if the integral on denom does not get evaluated. However, I cannot find a way to do that on Sage and Sage always tries to evaluate it (without success). Is there a way to tell Sage to keep it as an integral?

Thanks