diff --git a/Cargo.toml b/Cargo.toml
index a37f332..bd9482b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,6 +2,7 @@
 name = "bakare"
 version = "0.1.0"
 authors = ["Cyryl Płotnicki <cyplo@cyplo.net>"]
+edition = "2018"
 
 [dependencies]
 walkdir = "2.2"
diff --git a/src/backup.rs b/src/backup.rs
index 72078c9..c76a5e7 100644
--- a/src/backup.rs
+++ b/src/backup.rs
@@ -1,7 +1,7 @@
+use crate::storage::Version;
 use std::fs;
 use std::io;
 use std::path::Path;
-use storage::Version;
 use walkdir::DirEntry;
 use walkdir::WalkDir;
 
@@ -30,7 +30,7 @@ impl<'a> Engine<'a> {
     }
 
     pub fn file_version(&self, path: &Path) -> Version {
-        Version(0)
+        Version::Newest
     }
 
     fn process_entry(&self, entry: &DirEntry) -> Result<(), io::Error> {
diff --git a/src/restore.rs b/src/restore.rs
index 77b3df1..eef0f67 100644
--- a/src/restore.rs
+++ b/src/restore.rs
@@ -1,7 +1,7 @@
+use crate::storage::Version;
 use std::fs;
 use std::io;
 use std::path::Path;
-use storage::Version;
 use walkdir::DirEntry;
 use walkdir::WalkDir;
 
@@ -28,7 +28,7 @@ impl<'a> Engine<'a> {
     }
 
     fn restore(&self, what: WhatToRestore) -> Result<(), io::Error> {
-        self.restore_as_of_version(what, Version(0))
+        self.restore_as_of_version(what, Version::Newest)
     }
 
     pub fn restore_as_of_version(&self, what: WhatToRestore, version: Version) -> Result<(), io::Error> {
diff --git a/src/storage.rs b/src/storage.rs
index 5cf7f03..279b186 100644
--- a/src/storage.rs
+++ b/src/storage.rs
@@ -2,11 +2,17 @@ use std::collections::HashMap;
 use std::collections::HashSet;
 
 #[derive(Copy, Clone, Debug, PartialOrd, PartialEq)]
-pub struct Version(pub u64);
+pub enum Version {
+    Newest,
+    Specific(u64),
+}
 
 impl Version {
     fn next(self) -> Self {
-        Version(self.0 + 1)
+        match self {
+            Version::Newest => Version::Newest,
+            Version::Specific(old) => Version::Specific(old + 1),
+        }
     }
 }
 
@@ -44,7 +50,7 @@ impl<'a> Index<'a> {
             self.file_paths.get(source_path).map_or_else(
                 || IndexPathEntry {
                     hash,
-                    version: Version(0),
+                    version: Version::Newest,
                     storage_path: format!("{:X?}", hash.0),
                 },
                 |old_entry| {
diff --git a/tests/system_tests.rs b/tests/system_tests.rs
index bcb60cf..0692d9d 100644
--- a/tests/system_tests.rs
+++ b/tests/system_tests.rs
@@ -1,10 +1,7 @@
-extern crate bakare;
-extern crate dir_diff;
-extern crate tempfile;
-
 use bakare::backup;
 use bakare::restore;
 use bakare::restore::WhatToRestore::SpecificPath;
+
 use dir_diff::is_different;
 use std::fs::File;
 use std::io::Error;