diff --git a/Sources/LeetCode/LeetCode.swift b/Sources/LeetCode/LeetCode.swift
index 6b21cff..7d597ce 100644
--- a/Sources/LeetCode/LeetCode.swift
+++ b/Sources/LeetCode/LeetCode.swift
@@ -37,11 +37,11 @@ enum LeetCode {
     }
 
     static func invertTree(_ root: TreeNode?) -> TreeNode? {
-        var invertedTree: TreeNode
-        if root?.left != nil || root?.right != nil {
-            guard let nodeVal = root?.val else {
-            }
-            invertedTree = TreeNode(nodeVal, root?.right, root?.left)
+        var invertedTree: TreeNode?
+        if let val = root?.val {
+            invertedTree = TreeNode(val, invertTree(root?.right), invertTree(root?.left))
+        } else {
+            invertedTree = root
         }
         return invertedTree
     }