Sterile neutrinos with keV mass are a well motivated warm dark matter candidate. Despite a variety of searches, there is still parameter space left for this scenario. A sterile neutrino can decay into an active neutrino and a photon. This process leads to a gamma-ray line at half the sterile neutrino mass, making this model testable using gamma-ray telescopes. In this work we have developed analysis tools for the Fermi GBM for line searches taking into account directional information and we searched for gamma-ray lines in the Galactic center region. We report no excess of events over the background and put constraints on the parameter space of sterile neutrino dark matter.