diff --git a/part/map_test.go b/part/map_test.go
index 55e23fe..85a0f91 100644
--- a/part/map_test.go
+++ b/part/map_test.go
@@ -368,19 +368,38 @@ func TestMapTxn(t *testing.T) {
 	assert.Equal(t, 88, v)
 	tree = txn.Commit()
 
-	// Transaction can be reused after commit
+	// Transaction can be reused after commit (singleton case)
+	assert.Nil(t, tree.tree.root)
+	assert.False(t, tree.hasTree)
 	txn.Set("baz", 99)
-	mp = maps.Collect(txn.All())
-	assert.Len(t, mp, 2)
-	assert.Equal(t, map[string]int{"bar": 88, "baz": 99}, mp)
 	mp = maps.Collect(tree.All())
 	assert.Len(t, mp, 1)
 	assert.Equal(t, map[string]int{"bar": 88}, mp)
+	mp = maps.Collect(txn.All())
+	assert.Len(t, mp, 2)
+	assert.Equal(t, map[string]int{"bar": 88, "baz": 99}, mp)
 
+	// Set again since All() bumps txnID
+	txn.Set("baz", 99)
 	tree = txn.Commit()
+
+	// Transaction can be reused after commit (non-singleton case)
+	assert.NotNil(t, tree.tree.root)
+	assert.True(t, tree.hasTree)
+	txn.Set("baz", 999)
+
 	mp = maps.Collect(tree.All())
 	assert.Len(t, mp, 2)
 	assert.Equal(t, map[string]int{"bar": 88, "baz": 99}, mp)
+
+	mp = maps.Collect(txn.All())
+	assert.Len(t, mp, 2)
+	assert.Equal(t, map[string]int{"bar": 88, "baz": 999}, mp)
+
+	tree = txn.Commit()
+	mp = maps.Collect(tree.All())
+	assert.Len(t, mp, 2)
+	assert.Equal(t, map[string]int{"bar": 88, "baz": 999}, mp)
 }
 
 func TestUint64Map(t *testing.T) {
diff --git a/part/tree.go b/part/tree.go
index 7134549..24ea5e6 100644
--- a/part/tree.go
+++ b/part/tree.go
@@ -19,7 +19,7 @@ type Tree[T any] struct {
 	size      int // the number of objects in the tree
 	opts      options
 	prevTxn   *atomic.Pointer[Txn[T]] // the previous txn for reusing the allocation
-	prevTxnID uint64                  // the transaction ID that produced this tree
+	nextTxnID uint64                  // the next transaction ID to use
 }
 
 // New constructs a new tree.
@@ -74,7 +74,7 @@ func (t *Tree[T]) Txn() *Txn[T] {
 	txn.rootWatch = t.rootWatch
 	txn.size = t.size
 	txn.prevTxn = t.prevTxn
-	txn.txnID = t.prevTxnID + 1
+	txn.txnID = t.nextTxnID
 	return txn
 }
 
diff --git a/part/txn.go b/part/txn.go
index b6f484e..4d4936d 100644
--- a/part/txn.go
+++ b/part/txn.go
@@ -65,7 +65,7 @@ func (txn *Txn[T]) Clone() Tree[T] {
 		rootWatch: txn.rootWatch,
 		size:      txn.size,
 		prevTxn:   txn.prevTxn,
-		prevTxnID: txn.txnID,
+		nextTxnID: txn.txnID,
 	}
 }
 
@@ -185,13 +185,14 @@ func (txn *Txn[T]) Commit() Tree[T] {
 		validateTree(txn.oldRoot, nil, nil, txn.txnID)
 		validateTree(txn.root, nil, txn.watches, txn.txnID)
 	}
+	txn.txnID++
 	t := Tree[T]{
 		opts:      txn.opts,
 		root:      txn.root,
 		rootWatch: newRootWatch,
 		size:      txn.size,
 		prevTxn:   txn.prevTxn,
-		prevTxnID: txn.txnID,
+		nextTxnID: txn.txnID,
 	}
 	// Store this txn in the tree to reuse the allocation next time.
 	t.prevTxn.Store(txn)