diff --git a/cv7/program.c b/cv7/program.c
index 266a371..5b330c1 100644
--- a/cv7/program.c
+++ b/cv7/program.c
@@ -32,10 +32,16 @@ struct tree* load_tree() {
     if (node->value[0] != '*') {
         node->left = load_tree();
         node->right = load_tree();
+
+        if (!node->left || !node->right) {
+            destroy_tree(node);
+            return NULL;
+        }
     }
     return node;
 }
 
+
 void run_tree(struct tree* tree) {
     if (!tree) {
         return;