Sterile neutrinos is one of the possible physics beyond the Standard Model motivated by neutrino oscillations. Stable at cosmological time-scale sterile neutrinos may serve as dark matter. Typically, with mass in keV range, the sterile neutrinos form Warm dark matter and radiatively decay in galaxies providing X-ray telescopes with a prominent signature. Extensive searches for the sterile neutrino dark matter significantly reduced viable regions in the model parameter space. However, the situation changes with just one new ingredient -- a scalar field with Yukawa coupling to the sterile neutrinos. This scalar modifies the sterile neutrino production in the early Universe. Depending on the scalar field dynamics it makes models with large(small) active-sterile mixing cosmologically viable(interesting)