  We examine the nature of Josephson junction between two identical
Fe-pnictides with anti-phase s-wave pairing. pi-phase shift is found if the
junction barrier is thick and the two Fe-pnictides are oriented in certain
directions relative to the interface. Our theory provides a possible
explanation for the observed half integer flux quantum transitions in a
niobium/polycrystal NdFeAsO loop, and attributes the pi-phase shift to
intergrain junctions of Fe-pnictides.
