diff --git a/hw/boards.h b/hw/boards.h
index 6374dd1..712d3cd 100644
--- a/hw/boards.h
+++ b/hw/boards.h
@@ -52,7 +52,7 @@
 extern QEMUMachine r2d_machine;
 
 /* sun4m.c */
-extern QEMUMachine ss5_machine, ss10_machine, ss600mp_machine;
+extern QEMUMachine ss5_machine, ss10_machine, ss600mp_machine, ss20_machine;
 
 /* sun4u.c */
 extern QEMUMachine sun4u_machine;