diff --git a/graphs_trees/tree_bfs/bfs_solution.ipynb b/graphs_trees/tree_bfs/bfs_solution.ipynb
index c4f09d3..f96815f 100644
--- a/graphs_trees/tree_bfs/bfs_solution.ipynb
+++ b/graphs_trees/tree_bfs/bfs_solution.ipynb
@@ -101,7 +101,7 @@
     "\n",
     "    def bfs(self, visit_func):\n",
     "        if self.root is None:\n",
-    "            raise Exception('root is None')\n",
+    "            raise TypeError('root is None')\n",
     "        queue = deque()\n",
     "        queue.append(self.root)\n",
     "        while queue:\n",