Doubt in proof of Prime Number Theorem in the book by Apostol

Question

I have been studying the proof of Prime Number Theorem as outlined in the book Introduction to Analytic Number Theory by Apostol. I came across the following lemma :

In the proof of this lemma, the author states:

If $z = x + i y$ and $| z |= R$ the integrand is dominated by

$$\left|\frac{u^{-z}}{z(z+1)\cdots(z+k)}\right| = \frac{u^{-x}}{|z||z+1|\cdots|z+k|}$$

I can't understand how $|u^{-z}| = u^{-x}$.

I know this seems like a stupid doubt but please help me understand what I am missing.