Spin wave transmission experiments are performed on a one-dimensional magnonic crystal (MC) where an injection pad for domain walls reverses the magnetization M of selected nanostripes independently from the otherwise saturated MC. The MC consists of a periodic array of 255-nm-wide permalloy nanostripes with an edge-to-edge separation of 45 nm. In the experiment and simulations, we find that a single nanostripe with antiparallel M performing opposite spin precession reduces significantly the transmission of long-wavelength spin waves. Our findings allow for the implementation and current-controlled operation of magnonic devices such as spin-wave-based logic on the nanoscale.