The jump of the Milnor number in the X_9 singularity class

The jump of the Milnor number of an isolated singularity $f_0$ is the minimal non-zero difference between the Milnor numbers of $f_0$ and one of its deformations $(f_s))\mathrm{.}$ We prove that for the singularities in the $X_9$ singularity class their jumps are equal to 2.