diff --git a/include/linux/rio.h b/include/linux/rio.h
index 4e37a7cf..4d50611 100644
--- a/include/linux/rio.h
+++ b/include/linux/rio.h
@@ -396,7 +396,7 @@
 };
 
 /* Architecture and hardware-specific functions */
-extern void rio_register_mport(struct rio_mport *);
+extern int rio_register_mport(struct rio_mport *);
 extern int rio_open_inb_mbox(struct rio_mport *, void *, int, int);
 extern void rio_close_inb_mbox(struct rio_mport *, int);
 extern int rio_open_outb_mbox(struct rio_mport *, void *, int, int);