diff --git a/src/tree.c b/src/tree.c
index 45d9bc6..3b1cadd 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -1480,10 +1480,11 @@ static struct _tree_node* tree_trun_left_then_right(struct _tree* self, struct _
 {
     assert(self != NULL);
     assert(root != NULL);
-    assert(root->left != NULL);
     struct _tree_node* node = root->left;
-
-    tree_turn_left(self, root->left);
+    if(node != NULL)
+    {
+        tree_turn_left(self, node);
+    }
     node = tree_turn_right(self, root);
     return node;
 }
@@ -1492,9 +1493,11 @@ static struct _tree_node* tree_trun_right_then_left(struct _tree* self, struct _
 {
     assert(self != NULL);
     assert(root != NULL);
-    assert(root->right != NULL);
     struct _tree_node* node = root->right;
-    tree_turn_right(self, root->right);
+    if(node != NULL)
+    {
+        tree_turn_right(self, node);
+    }
     node = tree_turn_left(self, root);
     return node;
 }
diff --git a/test/tree_test.c b/test/tree_test.c
index 8328878..27f772c 100644
--- a/test/tree_test.c
+++ b/test/tree_test.c
@@ -279,8 +279,8 @@ void tree_test(void)
 void test_tree_num(void)
 {
     uint32_t i = 0;
-    int data[] = { 1,2,3,4,5,6};
-    // int data[] = { 5,2,3,1,7,8,6 };
+    // int data[] = { 1,2,3,4,5,6};
+    int data[] = { 5,2,3,1,7,8,6 };
     int temp = 0;
     uint32_t len = sizeof(data) / sizeof(data[0]);