diff --git a/src/runtime2/branch.rs b/src/runtime2/branch.rs
index 8f156102d6828c75c8a77f8b7bdb5dc15b3f46c8..297585f7909df4eb0857c86295c3e2782ff1e78c 100644
--- a/src/runtime2/branch.rs
+++ b/src/runtime2/branch.rs
@@ -3,7 +3,7 @@ use std::ops::{Index, IndexMut};
 
 use crate::protocol::ComponentState;
 use crate::protocol::eval::{Value, ValueGroup};
-use crate::runtime2::port::{Port, PortIdLocal};
+use crate::runtime2::port::PortIdLocal;
 
 /// Generic branch ID. A component will always have one branch: the
 /// non-speculative branch. This branch has ID 0. Hence in a speculative context
@@ -78,14 +78,14 @@ impl Branch {
     /// parent of the new branch within the execution tree.
     fn new_sync(new_index: u32, parent_branch: &Branch) -> Self {
         debug_assert!(
-            (parent_branch.sync_state == SpeculativeState::RunningNonSync && !parent_branch.parent_index.is_valid()) ||
-                (parent_branch.sync_state == SpeculativeState::HaltedAtBranchPoint)
-        );
+            (parent_branch.sync_state == SpeculativeState::RunningNonSync && !parent_branch.parent_id.is_valid()) ||
+            (parent_branch.sync_state == SpeculativeState::HaltedAtBranchPoint)
+        ); // forking from non-sync, or forking from a branching point
         debug_assert!(parent_branch.prepared_channel.is_none());
 
         Branch {
             id: BranchId::new(new_index),
-            parent_id: parent_branch.index,
+            parent_id: parent_branch.id,
             code_state: parent_branch.code_state.clone(),
             sync_state: SpeculativeState::RunningInSync,
             awaiting_port: parent_branch.awaiting_port,
@@ -130,7 +130,7 @@ impl BranchQueue {
 
 const NUM_QUEUES: usize = 3;
 
-#[derive(PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq)]
 pub(crate) enum QueueKind {
     Runnable,
     AwaitingMessage,
@@ -160,7 +160,7 @@ pub(crate) struct ExecTree {
     // All branches. the `parent_id` field in each branch implies the shape of
     // the tree. Branches are index stable throughout a sync round.
     pub branches: Vec<Branch>,
-    pub queues: [BranchQueue; NUM_QUEUES]
+    queues: [BranchQueue; NUM_QUEUES]
 }
 
 impl ExecTree {
@@ -235,7 +235,7 @@ impl ExecTree {
                 branch.next_in_queue.index as usize
             },
             None => {
-                queue.first as usize
+                queue.first.index as usize
             }
         };
 
@@ -322,7 +322,7 @@ impl IndexMut<BranchId> for ExecTree {
     }
 }
 
-pub struct BranchQueueIter<'a> {
+pub(crate) struct BranchQueueIter<'a> {
     branches: &'a [Branch],
     index: usize,
 }
@@ -342,7 +342,7 @@ impl<'a> Iterator for BranchQueueIter<'a> {
     }
 }
 
-pub struct BranchParentIter<'a> {
+pub(crate) struct BranchParentIter<'a> {
     branches: &'a [Branch],
     index: usize,
 }