diff --git a/lib/src/local_backend.rs b/lib/src/local_backend.rs
index a38fcaa6b..a3f674f09 100644
--- a/lib/src/local_backend.rs
+++ b/lib/src/local_backend.rs
@@ -279,6 +279,7 @@ pub fn commit_to_proto(commit: &Commit) -> crate::protos::local_store::Commit {
     for predecessor in &commit.predecessors {
         proto.predecessors.push(predecessor.to_bytes());
     }
+    proto.uses_tree_conflict_format = commit.uses_tree_conflict_format;
     let conflict = crate::protos::local_store::TreeConflict {
         removes: commit
             .root_tree
@@ -314,7 +315,7 @@ fn commit_from_proto(proto: crate::protos::local_store::Commit) -> Commit {
         parents,
         predecessors,
         root_tree,
-        uses_tree_conflict_format: true,
+        uses_tree_conflict_format: proto.uses_tree_conflict_format,
         change_id,
         description: proto.description,
         author: signature_from_proto(proto.author.unwrap_or_default()),
diff --git a/lib/src/protos/local_store.proto b/lib/src/protos/local_store.proto
index 9186e17ec..7e8a1d9ee 100644
--- a/lib/src/protos/local_store.proto
+++ b/lib/src/protos/local_store.proto
@@ -48,6 +48,8 @@ message Commit {
   repeated bytes parents = 1;
   repeated bytes predecessors = 2;
   TreeConflict root_tree = 3;
+  // TODO(#1624): delete when all code paths can handle this format
+  bool uses_tree_conflict_format = 8;
   bytes change_id = 4;
   string description = 5;
 
diff --git a/lib/src/protos/local_store.rs b/lib/src/protos/local_store.rs
index 9ead47759..13c09c1d4 100644
--- a/lib/src/protos/local_store.rs
+++ b/lib/src/protos/local_store.rs
@@ -61,6 +61,9 @@ pub struct Commit {
     pub predecessors: ::prost::alloc::vec::Vec<::prost::alloc::vec::Vec<u8>>,
     #[prost(message, optional, tag = "3")]
     pub root_tree: ::core::option::Option<TreeConflict>,
+    /// TODO(#1624): delete when all code paths can handle this format
+    #[prost(bool, tag = "8")]
+    pub uses_tree_conflict_format: bool,
     #[prost(bytes = "vec", tag = "4")]
     pub change_id: ::prost::alloc::vec::Vec<u8>,
     #[prost(string, tag = "5")]