diff --git a/kernel/power/user.c b/kernel/power/user.c
index 24d7d78..d65305b 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -99,6 +99,8 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf,
 	ssize_t res;
 
 	data = filp->private_data;
+	if (!data->ready)
+		return -ENODATA;
 	res = snapshot_read_next(&data->handle, count);
 	if (res > 0) {
 		if (copy_to_user(buf, data_of(data->handle), res))
@@ -245,7 +247,7 @@ static int snapshot_ioctl(struct inode *inode, struct file *filp,
 		break;
 
 	case SNAPSHOT_UNFREEZE:
-		if (!data->frozen)
+		if (!data->frozen || data->ready)
 			break;
 		mutex_lock(&pm_mutex);
 		thaw_processes();