diff --git a/src/main.rs b/src/main.rs
index 40fa22a..f05b94f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -299,7 +299,7 @@ fn main() -> Result<(), Error> {
         KeepModes::Save => mode_save(&mut cmd, args, ids, tags, conn, data_path)?,
         KeepModes::Get => mode_get(&mut cmd, args, ids, tags, &mut conn, data_path)?,
         KeepModes::List => mode_list(&mut cmd, args, ids, tags, &mut conn, data_path)?,
-        KeepModes::Update => mode_update(&mut cmd, args, ids, tags, &mut conn)?,
+        KeepModes::Update => mode_update(&mut cmd, args, ids, tags, &mut conn, data_path)?,
         KeepModes::Info => mode_info(&mut cmd, args, ids, tags, &mut conn, data_path)?,
         KeepModes::Delete => mode_delete(&mut cmd, args, ids, tags, &mut conn, data_path)?,
         KeepModes::Status => mode_status(&mut cmd, args, data_path, db_path)?,
@@ -596,7 +596,7 @@ fn mode_list(cmd: &mut Command, args: Args, ids: &mut Vec<i64>, tags: &Vec<Strin
 }
 
 
-fn mode_update(cmd: &mut Command, args: Args, ids: &mut Vec<i64>, tags: &mut Vec<String>, conn: &mut Connection) -> Result<()> {
+fn mode_update(cmd: &mut Command, args: Args, ids: &mut Vec<i64>, tags: &mut Vec<String>, conn: &mut Connection, data_path: PathBuf) -> Result<()> {
     if ids.is_empty() {
         cmd.error(ErrorKind::InvalidValue, "No ID given, you must supply exactly one ID when using --update").exit();
     } else if ids.len() > 1 {
@@ -606,7 +606,7 @@ fn mode_update(cmd: &mut Command, args: Args, ids: &mut Vec<i64>, tags: &mut Vec
     let item_id = ids.iter().next().expect("Unable to determine item id");
     let item_maybe = db::get_item(conn, *item_id)?;
 
-    let item = item_maybe.expect("Unable to find item in database");
+    let mut item = item_maybe.expect("Unable to find item in database");
     debug!("MAIN: Found item {:?}", item);
 
     if ! tags.is_empty() {
@@ -614,6 +614,24 @@ fn mode_update(cmd: &mut Command, args: Args, ids: &mut Vec<i64>, tags: &mut Vec
         db::set_item_tags(conn, item.clone(), tags)?;
     }
 
+    if item.size.is_none() {
+        info!("Updating unknown stream size");
+        let mut item_path = data_path.clone();
+        item_path.push(item.id.unwrap().to_string());
+        let item_file_metadata = item_path.metadata();
+
+        if item_file_metadata.is_ok() {
+            debug!("MAIN: Updating stream size of {:?}", item_path);
+            let compression_type = CompressionType::from_str(&item.compression)?;
+            let compression_engine = compression::get_engine(compression_type).expect("Unable to get compression engine");
+            let size = compression_engine.size(item_path)? as i64;
+            item.size = Some(size);
+            db::update_item(&conn, item.clone())?;
+        } else {
+            debug!("MAIN: Unable to update size of item due to missing file {:?}", item_path);
+        }
+    }
+
     if args.item.meta.len() > 0 {
         debug!("MAIN: Updating item meta");
         for kv in args.item.meta.iter() {