diff --git a/docs/index.js b/docs/index.js
index af3c94e..a7e4cd7 100644
--- a/docs/index.js
+++ b/docs/index.js
@@ -86,12 +86,13 @@ function parse() {
   if (isValid) {
     $grammarValidation.removeClass('editor-validation-invalid').text('Valid').show();
 
+    codeAst.insert(data.ast);
+    codeAstOptimized.insert(data.astOptimized);
+    $codeValidation.removeClass('editor-validation-invalid').text('Valid').show();
+
     const isValid = data.code.length === 0;
-    if (isValid) {
-      codeAst.insert(data.ast);
-      codeAstOptimized.insert(data.astOptimized);
-      $codeValidation.removeClass('editor-validation-invalid').text('Valid').show();
-    } else {
+
+    if (!isValid) {
       const html = generateErrorListHTML(data.code);
       $codeInfo.html(html);
       $codeValidation.addClass('editor-validation-invalid').text('Invalid').show();
diff --git a/docs/native.cpp b/docs/native.cpp
index db37a8f..6c37012 100644
--- a/docs/native.cpp
+++ b/docs/native.cpp
@@ -43,7 +43,7 @@ bool parse_grammar(const std::string &text, peg::parser &peg,
   return ret;
 }
 
-bool parse_code(const std::string &text, peg::parser &peg, std::string &json,
+void parse_code(const std::string &text, peg::parser &peg, std::string &json,
                 std::shared_ptr<peg::Ast> &ast) {
   peg.enable_ast();
   bool init;
@@ -51,7 +51,6 @@ bool parse_code(const std::string &text, peg::parser &peg, std::string &json,
   json += "[";
   auto ret = peg.parse_n(text.data(), text.size(), ast);
   json += "]";
-  return ret;
 }
 
 inline std::vector<std::string> splitRulesText(const std::string &s) {
@@ -78,7 +77,8 @@ std::string lint(const std::string &grammarText, const std::string &codeText,
 
   if (ret && peg) {
     std::shared_ptr<peg::Ast> ast;
-    if (parse_code(codeText, peg, codeResult, ast)) {
+    parse_code(codeText, peg, codeResult, ast);
+    if (ast) {
       astResult = escape_json(peg::ast_to_s(ast));
       auto rules = splitRulesText(opt_rules_text);
       astResultOptimized = escape_json(
diff --git a/docs/native.wasm b/docs/native.wasm
index 453ead5..05f6ec5 100644
Binary files a/docs/native.wasm and b/docs/native.wasm differ
diff --git a/peglib.h b/peglib.h
index 4d557d1..1f88483 100644
--- a/peglib.h
+++ b/peglib.h
@@ -3105,7 +3105,7 @@ private:
 
     g["Sequence"] = [&](const SemanticValues &vs) {
       if (vs.empty()) {
-        return lit("");
+        return npd(lit(""));
       } else if (vs.size() == 1) {
         return std::any_cast<std::shared_ptr<Ope>>(vs[0]);
       } else {