diff --git a/sys/ia64/include/bus.h b/sys/ia64/include/bus.h
index b44c72da507..d779da0bbca 100644
--- a/sys/ia64/include/bus.h
+++ b/sys/ia64/include/bus.h
@@ -124,8 +124,11 @@ int	bus_space_map(bus_space_tag_t t, bus_addr_t addr, bus_size_t size,
  * Unmap a region of device bus space.
  */
 
-void	bus_space_unmap(bus_space_tag_t t, bus_space_handle_t bsh,
-			bus_size_t size);
+static __inline void
+bus_space_unmap(bus_space_tag_t t __unused, bus_space_handle_t bsh __unused,
+                bus_size_t size __unused)
+{
+}
 
 /*
  * Get a new handle for a subregion of an already-mapped area of bus space.