diff --git a/drivers/misc/cros_ec_sandbox.c b/drivers/misc/cros_ec_sandbox.c
index 429f1a9b26..4fcb2d96f5 100644
--- a/drivers/misc/cros_ec_sandbox.c
+++ b/drivers/misc/cros_ec_sandbox.c
@@ -313,13 +313,15 @@ static int process_cmd(struct ec_state *ec,
 
 		switch (req->op) {
 		case EC_VBNV_CONTEXT_OP_READ:
+			/* TODO(sjg@chromium.org): Support full-size context */
 			memcpy(resp->block, ec->vbnv_context,
-			       sizeof(resp->block));
-			len = sizeof(*resp);
+			       EC_VBNV_BLOCK_SIZE);
+			len = 16;
 			break;
 		case EC_VBNV_CONTEXT_OP_WRITE:
-			memcpy(ec->vbnv_context, resp->block,
-			       sizeof(resp->block));
+			/* TODO(sjg@chromium.org): Support full-size context */
+			memcpy(ec->vbnv_context, req->block,
+			       EC_VBNV_BLOCK_SIZE);
 			len = 0;
 			break;
 		default: