diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 7fa23a6..d921d7b 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -11,7 +11,7 @@
 #include <linux/nfs_page.h>
 #include <linux/wait_bit.h>
 
-#define NFS_SB_MASK (SB_NOSUID|SB_NODEV|SB_NOEXEC|SB_SYNCHRONOUS)
+#define NFS_SB_MASK (SB_RDONLY|SB_NOSUID|SB_NODEV|SB_NOEXEC|SB_SYNCHRONOUS)
 
 extern const struct export_operations nfs_export_ops;