diff --git a/lib/src/default_index/composite.rs b/lib/src/default_index/composite.rs
index 40ae4e85a..24bb13ee1 100644
--- a/lib/src/default_index/composite.rs
+++ b/lib/src/default_index/composite.rs
@@ -483,12 +483,6 @@ impl Index for &CompositeIndex {
             .collect()
     }
 
-    fn topo_order(&self, input: &mut dyn Iterator<Item = &CommitId>) -> Vec<CommitId> {
-        let mut ids = input.cloned().collect_vec();
-        ids.sort_by_cached_key(|id| self.commit_id_to_pos(id).unwrap());
-        ids
-    }
-
     fn evaluate_revset<'index>(
         &'index self,
         expression: &ResolvedExpression,
diff --git a/lib/src/default_index/mutable.rs b/lib/src/default_index/mutable.rs
index 67cc2dfbf..efb91b185 100644
--- a/lib/src/default_index/mutable.rs
+++ b/lib/src/default_index/mutable.rs
@@ -504,10 +504,6 @@ impl Index for DefaultMutableIndex {
         self.as_composite().heads(candidates)
     }
 
-    fn topo_order(&self, input: &mut dyn Iterator<Item = &CommitId>) -> Vec<CommitId> {
-        self.as_composite().topo_order(input)
-    }
-
     fn evaluate_revset<'index>(
         &'index self,
         expression: &ResolvedExpression,
diff --git a/lib/src/default_index/readonly.rs b/lib/src/default_index/readonly.rs
index 8365b4558..8a88ee435 100644
--- a/lib/src/default_index/readonly.rs
+++ b/lib/src/default_index/readonly.rs
@@ -607,10 +607,6 @@ impl Index for DefaultReadonlyIndex {
         self.as_composite().heads(candidates)
     }
 
-    fn topo_order(&self, input: &mut dyn Iterator<Item = &CommitId>) -> Vec<CommitId> {
-        self.as_composite().topo_order(input)
-    }
-
     fn evaluate_revset<'index>(
         &'index self,
         expression: &ResolvedExpression,
diff --git a/lib/src/index.rs b/lib/src/index.rs
index cc00e9b8a..70d8880eb 100644
--- a/lib/src/index.rs
+++ b/lib/src/index.rs
@@ -116,10 +116,6 @@ pub trait Index: Send + Sync {
     /// `candidates` list it will appear at most once in the output.
     fn heads(&self, candidates: &mut dyn Iterator<Item = &CommitId>) -> Vec<CommitId>;
 
-    /// Orders a list of commit IDs such that parent commits appear before any
-    /// of their children. Commit IDs in the `input` are not deduplicated.
-    fn topo_order(&self, input: &mut dyn Iterator<Item = &CommitId>) -> Vec<CommitId>;
-
     /// Resolves the revset `expression` against the index and corresponding
     /// `store`.
     fn evaluate_revset<'index>(