diff --git a/cli/src/commands/debug.rs b/cli/src/commands/debug.rs
index 3794cd0a8..8583f29e2 100644
--- a/cli/src/commands/debug.rs
+++ b/cli/src/commands/debug.rs
@@ -18,7 +18,7 @@ use std::io::Write as _;
 
 use clap::Subcommand;
 use jj_lib::backend::ObjectId;
-use jj_lib::default_index_store::{DefaultIndexStore, ReadonlyIndexWrapper};
+use jj_lib::default_index_store::{DefaultIndexStore, DefaultReadonlyIndex};
 use jj_lib::local_working_copy::LocalWorkingCopy;
 use jj_lib::revset;
 use jj_lib::working_copy::WorkingCopy;
@@ -199,9 +199,10 @@ fn cmd_debug_index(
 ) -> Result<(), CommandError> {
     let workspace_command = command.workspace_helper(ui)?;
     let repo = workspace_command.repo();
-    let index_impl: Option<&ReadonlyIndexWrapper> = repo.readonly_index().as_any().downcast_ref();
-    if let Some(index_impl) = index_impl {
-        let stats = index_impl.as_composite().stats();
+    let default_index: Option<&DefaultReadonlyIndex> =
+        repo.readonly_index().as_any().downcast_ref();
+    if let Some(default_index) = default_index {
+        let stats = default_index.as_composite().stats();
         writeln!(ui.stdout(), "Number of commits: {}", stats.num_commits)?;
         writeln!(ui.stdout(), "Number of merges: {}", stats.num_merges)?;
         writeln!(
@@ -238,15 +239,15 @@ fn cmd_debug_reindex(
     if let Some(default_index_store) = default_index_store {
         default_index_store.reinit();
         let repo = repo.reload_at(repo.operation())?;
-        let index_impl: &ReadonlyIndexWrapper = repo
+        let default_index: &DefaultReadonlyIndex = repo
             .readonly_index()
             .as_any()
             .downcast_ref()
-            .expect("Default index should be a ReadonlyIndexWrapper");
+            .expect("Default index should be a DefaultReadonlyIndex");
         writeln!(
             ui.stderr(),
             "Finished indexing {:?} commits.",
-            index_impl.as_composite().stats().num_commits
+            default_index.as_composite().stats().num_commits
         )?;
     } else {
         return Err(user_error(format!(
diff --git a/lib/src/default_index_store.rs b/lib/src/default_index_store.rs
index 4eed2fd67..aa5dc18cf 100644
--- a/lib/src/default_index_store.rs
+++ b/lib/src/default_index_store.rs
@@ -238,7 +238,7 @@ impl IndexStore for DefaultIndexStore {
         } else {
             self.index_at_operation(store, op).unwrap()
         };
-        Box::new(ReadonlyIndexWrapper(index_impl))
+        Box::new(DefaultReadonlyIndex(index_impl))
     }
 
     fn write_index(
@@ -259,7 +259,7 @@ impl IndexStore for DefaultIndexStore {
                     "Failed to associate commit index file with a operation {op_id:?}: {err}"
                 ))
             })?;
-        Ok(Box::new(ReadonlyIndexWrapper(index)))
+        Ok(Box::new(DefaultReadonlyIndex(index)))
     }
 }
 
@@ -385,9 +385,11 @@ pub(crate) struct ReadonlyIndexImpl {
     overflow_parent: Vec<u8>,
 }
 
-pub struct ReadonlyIndexWrapper(Arc<ReadonlyIndexImpl>);
+/// Commit index backend which stores data on local disk.
+#[derive(Debug)]
+pub struct DefaultReadonlyIndex(Arc<ReadonlyIndexImpl>);
 
-impl ReadonlyIndex for ReadonlyIndexWrapper {
+impl ReadonlyIndex for DefaultReadonlyIndex {
     fn as_any(&self) -> &dyn Any {
         self
     }
@@ -410,7 +412,7 @@ impl Debug for ReadonlyIndexImpl {
     }
 }
 
-impl ReadonlyIndexWrapper {
+impl DefaultReadonlyIndex {
     pub fn as_composite(&self) -> CompositeIndex {
         self.0.as_composite()
     }
@@ -704,8 +706,8 @@ impl MutableIndex for MutableIndexImpl {
     fn merge_in(&mut self, other: &dyn ReadonlyIndex) {
         let other = other
             .as_any()
-            .downcast_ref::<ReadonlyIndexWrapper>()
-            .expect("index to merge in must be a ReadonlyIndexWrapper");
+            .downcast_ref::<DefaultReadonlyIndex>()
+            .expect("index to merge in must be a DefaultReadonlyIndex");
 
         let mut maybe_own_ancestor = self.parent_file.clone();
         let mut maybe_other_ancestor = Some(other.0.clone());
diff --git a/lib/tests/test_default_revset_graph_iterator.rs b/lib/tests/test_default_revset_graph_iterator.rs
index 1b4422474..7a3912d1d 100644
--- a/lib/tests/test_default_revset_graph_iterator.rs
+++ b/lib/tests/test_default_revset_graph_iterator.rs
@@ -14,7 +14,7 @@
 
 use itertools::Itertools;
 use jj_lib::commit::Commit;
-use jj_lib::default_index_store::ReadonlyIndexWrapper;
+use jj_lib::default_index_store::DefaultReadonlyIndex;
 use jj_lib::default_revset_engine::{evaluate, RevsetImpl};
 use jj_lib::repo::{ReadonlyRepo, Repo as _};
 use jj_lib::revset::ResolvedExpression;
@@ -29,7 +29,7 @@ fn revset_for_commits<'index>(
     let index = repo
         .readonly_index()
         .as_any()
-        .downcast_ref::<ReadonlyIndexWrapper>()
+        .downcast_ref::<DefaultReadonlyIndex>()
         .unwrap()
         .as_composite();
     let expression =
diff --git a/lib/tests/test_index.rs b/lib/tests/test_index.rs
index 9a0248c63..b6ed8bb5c 100644
--- a/lib/tests/test_index.rs
+++ b/lib/tests/test_index.rs
@@ -18,7 +18,7 @@ use jj_lib::backend::CommitId;
 use jj_lib::commit::Commit;
 use jj_lib::commit_builder::CommitBuilder;
 use jj_lib::default_index_store::{
-    CompositeIndex, IndexPosition, MutableIndexImpl, ReadonlyIndexWrapper,
+    CompositeIndex, DefaultReadonlyIndex, IndexPosition, MutableIndexImpl,
 };
 use jj_lib::index::Index as _;
 use jj_lib::repo::{MutableRepo, ReadonlyRepo, Repo};
@@ -446,7 +446,7 @@ fn create_n_commits(
 fn as_readonly_composite(repo: &Arc<ReadonlyRepo>) -> CompositeIndex<'_> {
     repo.readonly_index()
         .as_any()
-        .downcast_ref::<ReadonlyIndexWrapper>()
+        .downcast_ref::<DefaultReadonlyIndex>()
         .unwrap()
         .as_composite()
 }