diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 6f48d670c9415ce610980e6288d118623cd237d1..806df746f1a93b5a06ca970735faa3e775c28566 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -38,8 +38,6 @@
  * which have been left busy at at service shutdown.
  */
 
-#define AUTOFS_DEV_IOCTL_SIZE	sizeof(struct autofs_dev_ioctl)
-
 typedef int (*ioctl_fn)(struct file *, struct autofs_sb_info *,
 			struct autofs_dev_ioctl *);
 
diff --git a/include/uapi/linux/auto_dev-ioctl.h b/include/uapi/linux/auto_dev-ioctl.h
index af107aa7b6851461c4d76e095a6bf58abff4ca16..744b3d0609687b82bb198ed76c158417c22f09f9 100644
--- a/include/uapi/linux/auto_dev-ioctl.h
+++ b/include/uapi/linux/auto_dev-ioctl.h
@@ -113,10 +113,10 @@ struct autofs_dev_ioctl {
 
 static inline void init_autofs_dev_ioctl(struct autofs_dev_ioctl *in)
 {
-	memset(in, 0, sizeof(struct autofs_dev_ioctl));
+	memset(in, 0, AUTOFS_DEV_IOCTL_SIZE);
 	in->ver_major = AUTOFS_DEV_IOCTL_VERSION_MAJOR;
 	in->ver_minor = AUTOFS_DEV_IOCTL_VERSION_MINOR;
-	in->size = sizeof(struct autofs_dev_ioctl);
+	in->size = AUTOFS_DEV_IOCTL_SIZE;
 	in->ioctlfd = -1;
 }