1 files changed, 3 insertions, 0 deletions
diff --git a/grammer.cpp b/grammer.cpp
index 55e31c8..22b874e 100644
--- a/grammer.cpp
+++ b/grammer.cpp
@@ -426,6 +426,9 @@ bool Compiler::FillTree()
  index_t to_fill{};
 
  while (!subTreeIsComplete(root_node_id, to_fill)) {
+  if (tokens_used >= tokens.size())
+   return false; // Unexpected end of program?
+
   auto& node {nodes[to_fill]};
   std::string next_child {bnf[node.type][node.variant][node.child_ids.size()]};
   if (next_child == tokens[tokens_used].type) { // add token directly