  A measurement of the form factors of charged kaon semileptonic decays is
presented, based on $4.4 \times 10^6$ $K^\pm \to \pi^0 e^\pm \nu_e$
($K^\pm_{e3}$) and $2.3 \times 10^6$ $K^\pm \to \pi^0 \mu^\pm \nu_{\mu}$
($K^\pm_{\mu3}$) decays collected in 2004 by the NA48/2 experiment. The results
are obtained with improved precision as compared to earlier measurements. The
combination of measurements in the $K^\pm_{e3}$ and $K^\pm_{\mu3}$ modes is
also presented.
