diff --git a/src/libafs/MakefileProto.SOLARIS.in b/src/libafs/MakefileProto.SOLARIS.in
index 1e6a2aa356..10d02b7b70 100644
--- a/src/libafs/MakefileProto.SOLARIS.in
+++ b/src/libafs/MakefileProto.SOLARIS.in
@@ -45,10 +45,14 @@ KDEFS= -D_KERNEL -DSYSV -dn ${ARCH_DEFS}
 <sunx86_510 sunx86_511>
 DBUG= -Wu,-save_args
 
-<sun4x_58 sun4x_59 sun4x_510 sun4x_511>
+<sun4x_58 sun4x_59 sun4x_510>
 KDEFS_32 = -xarch=v8
 KDEFS_64 = -xarch=v9 
 
+<sun4x_511>
+KDEFS_32 =
+KDEFS_64 = -m64
+
 <sunx86_58 sunx86_59 sunx86_510>
 KDEFS_32 = 
 KDEFS_64 = -xarch=amd64 -xmodel=kernel