diff --git a/Dockerfile b/Dockerfile
index dac2be8..33a0451 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,7 +3,7 @@ RUN apk add --no-cache tzdata openssl
 WORKDIR /app
 ARG VCS_REF=development
 LABEL org.opencontainers.image.title="MangaCircus" org.opencontainers.image.revision=$VCS_REF
-COPY package.json server.js library.js reading-direction.js chapter-identity.js chapter-dates.js reading-analytics.js reading-access.js catalog.js backup.js ./
+COPY package.json server.js library.js reading-direction.js chapter-identity.js chapter-dates.js reading-analytics.js reading-access.js catalog.js backup.js moments.js ./
 COPY public ./public
 COPY greatest ./greatest
 COPY discovery ./discovery
diff --git a/test/dockerfile.test.js b/test/dockerfile.test.js
new file mode 100644
index 0000000..4327071
--- /dev/null
+++ b/test/dockerfile.test.js
@@ -0,0 +1,22 @@
+'use strict';
+// The image copies top-level modules by name; a new module missing there crashes the reader at start.
+const test = require('node:test'), assert = require('node:assert/strict');
+const fs = require('fs'), path = require('path');
+const root = path.resolve(__dirname, '..');
+
+test('every top-level module the reader requires is copied into the image', () => {
+  const dockerfile = fs.readFileSync(path.join(root, 'Dockerfile'), 'utf8');
+  const copied = new Set(dockerfile.split('\n').filter(line => line.startsWith('COPY ')).flatMap(line => line.split(/\s+/).slice(1, -1)));
+  const pending = ['server.js'], seen = new Set();
+  while (pending.length) {
+    const file = pending.pop();
+    if (seen.has(file)) continue;
+    seen.add(file);
+    for (const [, name] of fs.readFileSync(path.join(root, file), 'utf8').matchAll(/require\('\.\/([\w.-]+?)(?:\.js)?'\)/g)) {
+      // A folder (e.g. ./greatest) is copied as a whole; only single files need their own name in COPY.
+      if (fs.existsSync(path.join(root, name)) && fs.statSync(path.join(root, name)).isDirectory()) assert.ok(copied.has(name), `${name}/ is not copied`);
+      else pending.push(name + '.js');
+    }
+  }
+  for (const file of seen) assert.ok(copied.has(file), `${file} is required but not copied by the Dockerfile`);
+});