diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 6528aa6621819f31fae18eb9d337b1cfd624ba3a..b67e12eb7ca916b5b2dbc86fc3f9c8c3f9f7ae48 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -515,7 +515,8 @@ static int write_buf(struct file *filp, const void *buf, u32 len, loff_t *off)
 	set_fs(KERNEL_DS);
 
 	while (pos < len) {
-		ret = vfs_write(filp, (char *)buf + pos, len - pos, off);
+		ret = vfs_write(filp, (__force const char __user *)buf + pos,
+				len - pos, off);
 		/* TODO handle that correctly */
 		/*if (ret == -ERESTARTSYS) {
 			continue;