diff --git a/browser/components/resistfingerprinting/test/browser/browser.ini b/browser/components/resistfingerprinting/test/browser/browser.ini
index cc5adcad044d5..0124998f41723 100644
--- a/browser/components/resistfingerprinting/test/browser/browser.ini
+++ b/browser/components/resistfingerprinting/test/browser/browser.ini
@@ -8,6 +8,7 @@ support-files =
   file_workerPerformance.js
   head.js
 
+[browser_block_mozAddonManager.js]
 [browser_navigator.js]
 [browser_netInfo.js]
 [browser_performanceAPI.js]
diff --git a/browser/components/resistfingerprinting/test/browser/browser_block_mozAddonManager.js b/browser/components/resistfingerprinting/test/browser/browser_block_mozAddonManager.js
new file mode 100644
index 0000000000000..ee094670983ee
--- /dev/null
+++ b/browser/components/resistfingerprinting/test/browser/browser_block_mozAddonManager.js
@@ -0,0 +1,35 @@
+/**
+ * Bug 1384330 - A test case for making sure the navigator.mozAddonManager will
+ *   be blocked when pref 'privacy.resistFingerprinting.block_mozAddonManager' is true.
+ */
+
+const TEST_PATH = "https://example.com/browser/browser/" +
+                  "components/resistfingerprinting/test/browser/"
+
+add_task(async function test() {
+  await SpecialPowers.pushPrefEnv({"set":
+    [["extensions.webapi.testing", true]]
+  });
+
+  for (let pref of [false, true]) {
+    await SpecialPowers.pushPrefEnv({"set":
+      [["privacy.resistFingerprinting.block_mozAddonManager", pref]]
+    });
+
+    let tab = await BrowserTestUtils.openNewForegroundTab(
+      gBrowser, TEST_PATH + "file_dummy.html");
+
+    await ContentTask.spawn(tab.linkedBrowser, pref, function(aPref) {
+      if (aPref) {
+        is(content.navigator.mozAddonManager, undefined,
+          "The navigator.mozAddonManager should not exist when the pref is on.");
+      } else {
+        ok(content.navigator.mozAddonManager,
+          "The navigator.mozAddonManager should exist when the pref is off.");
+      }
+    });
+
+    await BrowserTestUtils.removeTab(tab);
+    await SpecialPowers.popPrefEnv();
+  }
+});
diff --git a/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp b/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp
index 3f2a7a5299f20..17ea9b0210cc3 100644
--- a/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp
+++ b/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp
@@ -20,6 +20,12 @@ using namespace mozilla::dom;
 
 static bool
 IsValidHost(const nsACString& host) {
+  // This hidden pref allows users to disable mozAddonManager entirely if they want
+  // for fingerprinting resistance. Someone like Tor browser will use this pref.
+  if (Preferences::GetBool("privacy.resistFingerprinting.block_mozAddonManager")) {
+    return false;
+  }
+
   // This is ugly, but Preferences.h doesn't have support
   // for default prefs or locked prefs
   nsCOMPtr<nsIPrefService> prefService (do_GetService(NS_PREFSERVICE_CONTRACTID));