diff --git a/drivers/io/io_block.c b/drivers/io/io_block.c
index 5d45c2f..b5e0e5f 100644
--- a/drivers/io/io_block.c
+++ b/drivers/io/io_block.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2023, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -271,7 +271,7 @@
 	block_size = cur->dev_spec->block_size;
 	assert((length <= cur->size) &&
 	       (length > 0U) &&
-	       (ops->read != 0));
+	       (ops->read != NULL));
 
 	/*
 	 * We don't know the number of bytes that we are going
@@ -383,8 +383,8 @@
 	block_size = cur->dev_spec->block_size;
 	assert((length <= cur->size) &&
 	       (length > 0U) &&
-	       (ops->read != 0) &&
-	       (ops->write != 0));
+	       (ops->read != NULL) &&
+	       (ops->write != NULL));
 
 	/*
 	 * We don't know the number of bytes that we are going