diff --git a/background.js b/background.js
index d1a28c3..33e2db5 100644
--- a/background.js
+++ b/background.js
@@ -1,4 +1,10 @@
 'use strict';
+// Cross-browser API namespace. Firefox provides Promise-based `browser.*`;
+// Chrome MV3 exposes `browser.*` too, but some builds only populate the
+// `chrome.*` global. Alias to whichever is present.
+if (typeof browser === 'undefined' || browser == null) {
+  var browser = (typeof chrome !== 'undefined' ? chrome : {});
+}
 
 function errMsg(err) {
   return String((err && err.message) || err);
diff --git a/content.js b/content.js
index 0da0d55..df2a3ad 100644
--- a/content.js
+++ b/content.js
@@ -1,6 +1,11 @@
 (function () {
   'use strict';
 
+  // Cross-browser API namespace (see background.js). No-op in Firefox.
+  if (typeof browser === 'undefined' || browser == null) {
+    var browser = (typeof chrome !== 'undefined' ? chrome : {});
+  }
+
   const MASTER_KEY = 'enabled';
 
   async function isEnabled() {
diff --git a/popup.js b/popup.js
index c601f31..0bcc0ef 100644
--- a/popup.js
+++ b/popup.js
@@ -1,5 +1,10 @@
 'use strict';
 
+// Cross-browser API namespace (see background.js). No-op in Firefox.
+if (typeof browser === 'undefined' || browser == null) {
+  var browser = (typeof chrome !== 'undefined' ? chrome : {});
+}
+
 const $ = (sel) => document.querySelector(sel);
 
 const MASTER_KEY = 'enabled';
diff --git a/scripts/build.js b/scripts/build.js
index 4adce7e..3ac86e0 100644
--- a/scripts/build.js
+++ b/scripts/build.js
@@ -23,8 +23,8 @@ function collectFiles(srcDir, out = [], prefix = '') {
     const abs = path.join(srcDir, entry);
     const rel = prefix ? prefix + '/' + entry : entry;
     if (entry === '.git' || entry === 'node_modules' || entry === 'dist' ||
-        entry === 'docs' || entry === 'scripts' || entry === 'manifest.json' ||
-        entry.startsWith('.')) {
+        entry === 'docs' || entry === 'scripts' || entry === 'test' ||
+        entry === 'manifest.json' || entry.startsWith('.')) {
       continue;
     }
     if (fs.statSync(abs).isDirectory()) collectFiles(abs, out, rel);