diff --git a/src/server/backups.rs b/src/server/backups.rs
index 66c7192..2620e17 100644
--- a/src/server/backups.rs
+++ b/src/server/backups.rs
@@ -38,9 +38,12 @@ fn files(src_dir: PathBuf) -> io::Result<HashSet<PathBuf>> {
     Ok(files)
 }
 
-/// Return false only if we can say with certainty that the file wasn't modified since the given
-/// timestamp, true otherwise.
-fn modified_since<T: AsRef<Path>>(time: chrono::DateTime<Utc>, path: T) -> bool {
+/// Check whether a file has been modified since the given timestamp.
+///
+/// Note that this function will *only* return true if it can determine with certainty that the
+/// file has not been modified. If any errors occur while obtaining the required metadata (e.g. if
+/// the file system does not support this metadata), this function will return false.
+fn not_modified_since<T: AsRef<Path>>(time: chrono::DateTime<Utc>, path: T) -> bool {
     let path = path.as_ref();
 
     if let Ok(metadata) = path.metadata() {
@@ -50,14 +53,14 @@ fn modified_since<T: AsRef<Path>>(time: chrono::DateTime<Utc>, path: T) -> bool
             let t: chrono::DateTime<Utc> = last_modified.into();
             let t = t.with_timezone(&Local);
 
-            return t >= time;
+            return t < time;
         }
     }
 
     false
 }
 
-#[derive(PartialEq)]
+#[derive(Debug, PartialEq)]
 pub enum BackupType {
     Full,
     Incremental,
@@ -71,6 +74,7 @@ pub enum BackupError {
 type BackupResult<T> = Result<T, BackupError>;
 
 /// Represents the changes relative to the previous backup
+#[derive(Debug)]
 pub struct BackupDelta {
     /// What files were added/modified in each part of the tarball.
     pub added: HashMap<PathBuf, HashSet<PathBuf>>,
@@ -142,6 +146,7 @@ impl BackupDelta {
 }
 
 /// Represents a successful backup
+#[derive(Debug)]
 pub struct Backup {
     previous: Option<Arc<Backup>>,
     /// When the backup was started (also corresponds to the name)
@@ -199,7 +204,7 @@ impl Backup {
             let files = files(src_dir.clone())?;
 
             for path in &files {
-                ar.append_path_with_name(dir_in_tar.join(path), src_dir.join(path))?;
+                ar.append_path_with_name(src_dir.join(path), dir_in_tar.join(path))?;
             }
 
             added.insert(dir_in_tar, files);
@@ -231,6 +236,7 @@ impl Backup {
         let enc = GzEncoder::new(tar_gz, Compression::default());
         let mut ar = tar::Builder::new(enc);
 
+        // TODO remove unwrap
         let previous_state = previous.state().unwrap();
         let mut delta = BackupDelta::new();
 
@@ -238,12 +244,14 @@ impl Backup {
             let files = files(src_dir.clone())?;
             let added_files = files
                 .iter()
-                .filter(|p| modified_since(previous.start_time, p))
+                // This explicit negation is because we wish to also include files for which we
+                // couldn't determine the last modified time
+                .filter(|p| !not_modified_since(previous.start_time, src_dir.join(p)))
                 .cloned()
                 .collect::<HashSet<PathBuf>>();
 
             for path in added_files.iter() {
-                ar.append_path_with_name(dir_in_tar.join(path), src_dir.join(path))?;
+                ar.append_path_with_name(src_dir.join(path), dir_in_tar.join(path))?;
             }
 
             delta.added.insert(dir_in_tar.clone(), added_files);
@@ -295,16 +303,13 @@ impl BackupManager {
             (PathBuf::from("worlds"), self.world_dir.clone()),
         ];
 
-        if let Some(last_backup) = &self.last_backup {
-            let clone = last_backup.clone();
-            self.last_backup = Some(Arc::new(Backup::create_from(
-                clone,
-                &self.backup_dir,
-                dirs,
-            )?));
+        let backup = if let Some(last_backup) = &self.last_backup {
+            Backup::create_from(Arc::clone(last_backup), &self.backup_dir, dirs)?
         } else {
-            self.last_backup = Some(Arc::new(Backup::create(&self.backup_dir, dirs)?));
-        }
+            Backup::create(&self.backup_dir, dirs)?
+        };
+
+        self.last_backup = Some(Arc::new(backup));
 
         Ok(())
     }