diff --git a/index.html b/index.html
index e0d0bb8..90f6229 100644
--- a/index.html
+++ b/index.html
@@ -12,13 +12,13 @@
     </title>
     <link rel="canonical" href="https://deployanyway.github.io/" />
     <link rel="icon" href="favicon.svg" type="image/svg+xml" />
-    <link rel="stylesheet" href="style-54d303f2.css?v=stable-1.0.2" />
+    <link rel="stylesheet" href="style-54d303f2.css?v=stable-1.0.3" />
     <script type="importmap">
       { "imports": { "node:util": "./browser-format.js" } }
     </script>
-    <script type="module" src="app-1.0.0.js?v=stable-1.0.2"></script>
-    <script type="module" src="siblings-1.0.0.js?v=stable-1.0.2"></script>
-    <script type="module" src="value-1.0.0.js?v=stable-1.0.2"></script>
+    <script type="module" src="app-1.0.0.js?v=stable-1.0.3"></script>
+    <script type="module" src="siblings-1.0.0.js?v=stable-1.0.3"></script>
+    <script type="module" src="value-1.0.0.js?v=stable-1.0.3"></script>
   </head>
   <body>
     <main>
@@ -369,3 +369,4 @@ <h2 id="feedback-title">Help us make the next release useful.</h2>
     </main>
   </body>
 </html>
+
diff --git a/value-1.0.0.js b/value-1.0.0.js
index 297e85e..0f2c033 100644
--- a/value-1.0.0.js
+++ b/value-1.0.0.js
@@ -378,6 +378,10 @@ panel(
     control("receipt-output", "Output", "readable", ["readable", "JSON"]),
   ],
   () => {
+    if (!/^\d+$/.test(val("receipt-build").trim()))
+      throw new TypeError(
+        "Provide an explicit nonnegative integer build exit code.",
+      );
     const meta = {
         commit: val("receipt-source-commit"),
         capturedAt: val("receipt-time"),