diff --git a/lib/src/backend.rs b/lib/src/backend.rs
index c7b3870f6..20738c55a 100644
--- a/lib/src/backend.rs
+++ b/lib/src/backend.rs
@@ -23,6 +23,8 @@ use thiserror::Error;
 use crate::content_hash::ContentHash;
 use crate::repo_path::{RepoPath, RepoPathComponent};
 
+pub const CHANGE_ID_HASH_LENGTH: usize = 16;
+
 pub trait ObjectId {
     fn new(value: Vec<u8>) -> Self;
     fn object_type(&self) -> String;
@@ -337,7 +339,7 @@ pub fn make_root_commit(empty_tree_id: TreeId) -> Commit {
         email: String::new(),
         timestamp,
     };
-    let change_id = ChangeId::new(vec![0; 16]);
+    let change_id = ChangeId::new(vec![0; CHANGE_ID_HASH_LENGTH]);
     Commit {
         parents: vec![],
         predecessors: vec![],
diff --git a/lib/src/settings.rs b/lib/src/settings.rs
index 7fa6d7db1..348f2f293 100644
--- a/lib/src/settings.rs
+++ b/lib/src/settings.rs
@@ -19,7 +19,7 @@ use chrono::DateTime;
 use rand::prelude::*;
 use rand_chacha::ChaCha20Rng;
 
-use crate::backend::{ChangeId, ObjectId, Signature, Timestamp};
+use crate::backend::{ChangeId, ObjectId, Signature, Timestamp, CHANGE_ID_HASH_LENGTH};
 
 #[derive(Debug, Clone)]
 pub struct UserSettings {
@@ -167,7 +167,7 @@ impl UserSettings {
 pub struct JJRng(Mutex<ChaCha20Rng>);
 impl JJRng {
     pub fn new_change_id(&self) -> ChangeId {
-        let random_bytes: [u8; 16] = self.gen();
+        let random_bytes: [u8; CHANGE_ID_HASH_LENGTH] = self.gen();
         ChangeId::new(random_bytes.into())
     }