diff --git a/06-linked-list/projects/finished/LinkedList.playground/Contents.swift b/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
index d41e150..82817f6 100644
--- a/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
+++ b/06-linked-list/projects/finished/LinkedList.playground/Contents.swift
@@ -38,7 +38,7 @@ example(of: "inserting at a particular index") {
   print("Before inserting: \(list)")
   var middleNode = list.node(at: 1)!
   for _ in 1...4 {
-    middleNode = list.insert(-1, after: middleNode)
+    middleNode = list.insert(-1, after: middleNode) ?? Node(value: 0)
   }
   print("After inserting: \(list)")
 }
@@ -129,4 +129,20 @@ example(of: "linked list cow") {
     list2.remove(after: node)
   }
   print("List2: \(list2)")
+    
+    print("Append node on list2")
+    list2.append(4)
+    print("List2: \(list2)")
+
+    print("Insert node on list2")
+    if let node2 = list2.node(at: 0) {
+      list2.insert(5, after: node2)
+    }
+    print("List2: \(list2)")
+
+    print("Removing middle node on list2")
+    if let node3 = list2.node(at: 1) {
+      list2.remove(after: node3)
+    }
+    print("List2: \(list2)")
 }
diff --git a/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift b/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
index ab44d82..0e49f2b 100644
--- a/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
+++ b/06-linked-list/projects/finished/LinkedList.playground/Sources/LinkedList.swift
@@ -41,8 +41,8 @@ public struct LinkedList<Value> {
   }
   
   @discardableResult
-  public mutating func insert(_ value: Value, after node: Node<Value>) -> Node<Value> {
-    copyNodes()
+  public mutating func insert(_ value: Value, after node: Node<Value>) -> Node<Value>? {
+    guard let node = copyNodes(returningCopyOf: node) else { return nil }
     guard tail !== node else {
       append(value)
       return tail!
@@ -117,7 +117,7 @@ public struct LinkedList<Value> {
   
   private mutating func copyNodes(returningCopyOf node: Node<Value>?) -> Node<Value>? {
     guard !isKnownUniquelyReferenced(&head) else {
-      return nil
+      return node
     }
     guard var oldNode = head else {
       return nil
@@ -135,6 +135,7 @@ public struct LinkedList<Value> {
       newNode = newNode!.next
       oldNode = nextOldNode
     }
+      tail = newNode
     
     return nodeCopy
   }