diff --git a/html/semantics/scripting-1/the-script-element/execution-timing/128.html b/html/semantics/scripting-1/the-script-element/execution-timing/128.html
index 39ec24f6816bd0..293c55add1cd5a 100644
--- a/html/semantics/scripting-1/the-script-element/execution-timing/128.html
+++ b/html/semantics/scripting-1/the-script-element/execution-timing/128.html
@@ -6,6 +6,7 @@
   <script src="testlib/testlib.js"></script>
 </head>
 <div id="log"></div>
+<p>This test is similar to <a href="151.html">151.html</a>, but here the parent script is flagged as non-parser-inserted in "prepare the script element" because it is empty.</p>
 <script>
   var t = async_test();
 </script>
diff --git a/html/semantics/scripting-1/the-script-element/execution-timing/151.html b/html/semantics/scripting-1/the-script-element/execution-timing/151.html
new file mode 100644
index 00000000000000..8880e4016e6b1b
--- /dev/null
+++ b/html/semantics/scripting-1/the-script-element/execution-timing/151.html
@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<html><head>
+  <title>scheduler: appending script element to non-parser-inserted script</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="testlib/testlib.js"></script>
+</head>
+<div id="log"></div>
+<p>This test is similar to <a href="128.html">128.html</a>, but here the parent script is non-parser-inserted all along.</p>
+<script>
+var t = async_test();
+t.step(function() {
+  log("inline script #1");
+  var script = document.createElement("script");
+  document.body.appendChild(script);
+
+  var frag = document.createDocumentFragment();
+  frag.appendChild(document.createTextNode("t.step(function() {log('inline script #2');\n"));
+  frag.appendChild(document.createElement("script")).textContent = "t.step(function() {log('inline script #3');});"
+  frag.appendChild(document.createTextNode("log('end inline script #2');})"));
+
+  script.appendChild(frag);
+  log("end inline script #1");
+});
+
+onload = t.step_func_done(function() {
+  assert_array_equals(eventOrder, ["inline script #1", "inline script #3", "inline script #2", "end inline script #2", "end inline script #1"]);
+});
+</script>
