diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 7cd56d2..a994129 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -389,6 +389,8 @@
 static inline int mtd_lock_user_prot_reg(struct mtd_info *mtd, loff_t from,
 					 size_t len)
 {
+	if (!mtd->lock_user_prot_reg)
+		return -EOPNOTSUPP;
 	return mtd->lock_user_prot_reg(mtd, from, len);
 }