diff --git a/testing/geckodriver/CHANGES.md b/testing/geckodriver/CHANGES.md
index c4f3c41461f9..25121b88ed19 100644
--- a/testing/geckodriver/CHANGES.md
+++ b/testing/geckodriver/CHANGES.md
@@ -7,6 +7,22 @@ All notable changes to this program is documented in this file.
 Unreleased
 ----------
 
+### Added
+
+- Added support for searching for Nightly’s default path on macOS
+
+  If the location of the Firefox binary is not given, geckodriver
+  will from now also look for the location of Firefox Nightly in
+  the default locations.  The ordered list of search paths on macOS
+  is as follows:
+
+    1. `/Applications/Firefox.app/Contents/MacOS/firefox-bin`
+    2. `$HOME/Applications/Firefox.app/Contents/MacOS/firefox-bin`
+    3. `/Applications/Firefox Nightly.app/Contents/MacOS/firefox-bin`
+    4. `$HOME/Applications/Firefox Nightly.app/Contents/MacOS/firefox-bin`
+
+  Thanks to [Kriti Singh] for this patch.
+
 ### Removed
 
 - Dropped support for legacy Selenium web element references
@@ -1194,6 +1210,7 @@ and greater.
 [Jeremy Lempereur]: https://github.com/o0Ignition0o
 [Joshua Bruning]: https://github.com/joshbruning
 [Kalpesh Krishna]: https://github.com/martiansideofthemoon
+[Kriti Singh]: https://github.com/kritisingh1
 [Mike Pennisi]: https://github.com/jugglinmike
 [Sven Jost]: https://github/mythsunwind
 [Vlad Filippov]: https://github.com/vladikoff
diff --git a/testing/geckodriver/doc/Capabilities.md b/testing/geckodriver/doc/Capabilities.md
index a0c0c89c7dff..2faa7bf31110 100644
--- a/testing/geckodriver/doc/Capabilities.md
+++ b/testing/geckodriver/doc/Capabilities.md
@@ -33,13 +33,16 @@ started and run. It may contain any of the following fields:
    to select which custom browser binary to use.
    If left undefined geckodriver will attempt
    to deduce the default location of Firefox
-   on the current system.
+   on the current system. If Firefox stable is
+   not installed, it will suggest the default
+   location of Firefox Nightly instead.
 
    <p>
    On macOS the path must be absolute to the browser binary,
-   e.g. <code>/Applications/Firefox.app/Contents/MacOS/firefox</code>.
+   e.g. <code>/Applications/Firefox.app/Contents/MacOS/firefox</code> or,
+   in case of Nightly, <code>/Applications/Firefox Nightly.app/Contents/MacOS/firefox</code>
    Specifying an application bundle such as <code>/Applications/Firefox.app</code>
-   will <em>not</em> work.
+   or <code>/Applications/Firefox Nightly.app</code> will <em>not</em> work.
  </tr>
 
  <tr id=capability-args>
diff --git a/testing/mozbase/rust/mozrunner/src/runner.rs b/testing/mozbase/rust/mozrunner/src/runner.rs
index ab3ed1da9674..9680c22de36d 100644
--- a/testing/mozbase/rust/mozrunner/src/runner.rs
+++ b/testing/mozbase/rust/mozrunner/src/runner.rs
@@ -315,8 +315,9 @@ pub mod platform {
     use std::path::PathBuf;
 
     /// Searches the system path for `firefox-bin`, then looks for
-    /// `Applications/Firefox.app/Contents/MacOS/firefox-bin` under both `/`
-    /// (system root) and the user home directory.
+    /// `Applications/Firefox.app/Contents/MacOS/firefox-bin` as well
+    /// as `Applications/Firefox Nightly.app/Contents/MacOS/firefox-bin`
+    /// under both `/` (system root) and the user home directory.
     pub fn firefox_default_path() -> Option<PathBuf> {
         if let Some(path) = find_binary("firefox-bin") {
             return Some(path);
@@ -324,11 +325,10 @@ pub mod platform {
 
         let home = dirs::home_dir();
         for &(prefix_home, trial_path) in [
-            (
-                false,
-                "/Applications/Firefox.app/Contents/MacOS/firefox-bin",
-            ),
+            (false, "/Applications/Firefox.app/Contents/MacOS/firefox-bin"),
             (true, "Applications/Firefox.app/Contents/MacOS/firefox-bin"),
+            (false, "/Applications/Firefox Nightly.app/Contents/MacOS/firefox-bin"),
+            (true, "Applications/Firefox Nightly.app/Contents/MacOS/firefox-bin"),
         ].iter()
         {
             let path = match (home.as_ref(), prefix_home) {