diff --git a/drivers/platform/olpc/olpc-ec.c b/drivers/platform/olpc/olpc-ec.c
index 4a2d36f7331e..063f7e55c421 100644
--- a/drivers/platform/olpc/olpc-ec.c
+++ b/drivers/platform/olpc/olpc-ec.c
@@ -269,7 +269,7 @@ static ssize_t ec_dbgfs_cmd_write(struct file *file, const char __user *buf,
 
 	mutex_lock(&ec_dbgfs_lock);
 
-	size = simple_write_to_buffer(cmdbuf, sizeof(cmdbuf), ppos, buf, size);
+	size = simple_write_to_buffer(cmdbuf, sizeof(cmdbuf) - 1, ppos, buf, size);
 
 	m = sscanf(cmdbuf, "%x:%u %x %x %x %x %x", &ec_cmd_int[0],
 			&ec_dbgfs_resp_bytes, &ec_cmd_int[1], &ec_cmd_int[2],