diff --git a/mobile/android/base/Tab.java b/mobile/android/base/Tab.java
index 2602d3f840a9..ac413c3e2577 100644
--- a/mobile/android/base/Tab.java
+++ b/mobile/android/base/Tab.java
@@ -179,6 +179,10 @@ public class Tab {
         return mUrl;
     }
 
+    /**
+     * Returns the base domain of the loaded uri. Note that if the page is
+     * a Reader mode uri, the base domain returned is that of the original uri.
+     */
     public String getBaseDomain() {
         return mBaseDomain;
     }
diff --git a/mobile/android/chrome/content/browser.js b/mobile/android/chrome/content/browser.js
index 53e5232016be..1a7f51f751a6 100644
--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -4430,7 +4430,11 @@ Tab.prototype = {
     this.clickToPlayPluginsActivated = false;
     // Borrowed from desktop Firefox: http://mxr.mozilla.org/mozilla-central/source/browser/base/content/urlbarBindings.xml#174
     let documentURI = contentWin.document.documentURIObject.spec
-    let matchedURL = documentURI.match(/^((?:[a-z]+:\/\/)?(?:[^\/]+@)?)(.+?)(?::\d+)?(?:\/|$)/);
+
+    // If reader mode, get the base domain for the original url.
+    let strippedURI = this._stripAboutReaderURL(documentURI);
+
+    let matchedURL = strippedURI.match(/^((?:[a-z]+:\/\/)?(?:[^\/]+@)?)(.+?)(?::\d+)?(?:\/|$)/);
     let baseDomain = "";
     if (matchedURL) {
       var domain = "";
@@ -4488,6 +4492,19 @@ Tab.prototype = {
     }
   },
 
+  _stripAboutReaderURL: function (url) {
+    if (!url.startsWith("about:reader")) {
+      return url;
+    }
+
+    // From ReaderParent._getOriginalUrl (browser/modules/ReaderParent.jsm).
+    let searchParams = new URLSearchParams(url.substring("about:reader?".length));
+    if (!searchParams.has("url")) {
+        return url;
+    }
+    return decodeURIComponent(searchParams.get("url"));
+  },
+
   // Properties used to cache security state used to update the UI
   _state: null,
   _hostChanged: false, // onLocationChange will flip this bit