diff --git a/bitbake/lib/toaster/tests/browser/README b/bitbake/lib/toaster/tests/browser/README
index f57154eda9..969f06cfc2 100644
--- a/bitbake/lib/toaster/tests/browser/README
+++ b/bitbake/lib/toaster/tests/browser/README
@@ -24,15 +24,30 @@ To run tests against PhantomJS (headless):
 * On *nix systems, put phantomjs on PATH
 * Not tested on Windows
 
-Firefox should work without requiring additional software to be installed.
+To run tests against Firefox, you may need to install the Marionette driver,
+depending on how new your version of Firefox is. One clue that you need to do
+this is if you see an exception like:
 
-The test case will instantiate a Selenium driver set by the
+  selenium.common.exceptions.WebDriverException: Message: The browser
+  appears to have exited before we could connect. If you specified
+  a log_file in the FirefoxBinary constructor, check it for details.
+
+See https://developer.mozilla.org/en-US/docs/Mozilla/QA/Marionette/WebDriver
+for installation instructions. Ensure that the Marionette executable (renamed
+as wires on Linux or wires.exe on Windows) is on your PATH; and use "marionette"
+as the browser string passed via TOASTER_TESTS_BROWSER (see below).
+
+(Note: The Toaster tests have been checked against Firefox 47 with the
+Marionette driver.)
+
+The test cases will instantiate a Selenium driver set by the
 TOASTER_TESTS_BROWSER environment variable, or Chrome if this is not specified.
 
 Available drivers:
 
 * chrome (default)
 * firefox
+* marionette (for newer Firefoxes)
 * ie
 * phantomjs