  We report on the timing properties of the `Crab twin' pulsar PSR~B0540$-$69
measured with X-ray data taken with the Swift telescope over a period of
1100\,days. The braking index of the pulsar was estimated to be $n =
0.03\pm0.013$ in a previous study performed in 2015 with 500-day Swift data.
This small value of $n$ is unusual for pulsars, and a comparison to old
measurements of $n\approx2.1$ for the same target determined $\sim$10 years ago
suggests a dramatic change in the braking index. To confirm the small value and
large change of $n$, we used 1100-day Swift observations including the data
used for measuring $n=0.03$. In this study we found that the braking index of
PSR~B0540$-$69 is $n=0.163\pm0.001$, somewhat larger than $0.03$. Since the
measured value of $n$ is still much smaller than $2.1$, we can confirm the
dramatic change in the braking index for this pulsar.
