diff --git a/src/database/schema/commit.rs b/src/database/schema/commit.rs
@@ -189,7 +189,7 @@ impl CommitTree {
pub fn fetch_latest_one(&self) -> Result<Option<YokedCommit>, anyhow::Error> {
let mut key = self.prefix.to_vec();
- key.extend_from_slice(&(self.len()? - 1).to_be_bytes());
+ key.extend_from_slice(&(self.len()?.saturating_sub(1)).to_be_bytes());
let cf = self
.db