That's because they are UNITCOMBAT_ARCHER not UNITCOMBAT_MOUNTED as they used to be. Civ5Buildings.xml confirms. Code: <Building_UnitCombatProductionModifiers> <Row> <BuildingType>BUILDING_STABLE</BuildingType> <UnitCombatType>UNITCOMBAT_MOUNTED</UnitCombatType> <Modifier>25</Modifier> </Row> </Building_UnitCombatProductionModifiers> Affected units are Chariot Archer, Indian warelephant, Egyptian war chariot, Arabian camel archer, Keshik. They were probably changed to unitcombat_archer to get rid of spearmen getting a bonus vs their ranged attack. However, as a result this broke them for the stable.