diff --git a/java/client/src/org/openqa/selenium/firefox/XpiDriverService.java b/java/client/src/org/openqa/selenium/firefox/XpiDriverService.java
index <HASH>..<HASH> 100644
--- a/java/client/src/org/openqa/selenium/firefox/XpiDriverService.java
+++ b/java/client/src/org/openqa/selenium/firefox/XpiDriverService.java
@@ -103,6 +103,9 @@ public class XpiDriverService extends DriverService {
   @Override
   protected void waitUntilAvailable() throws MalformedURLException {
     try {
+      // Use a longer timeout, because 45 seconds was the default timeout in the predecessor to
+      // XpiDriverService. This has to wait for Firefox to start, not just a service, and some users
+      // may be running tests on really slow machines.
       URL status = new URL(getUrl(port).toString() + "/status");
       new UrlChecker().waitUntilAvailable(45, SECONDS, status);
     } catch (UrlChecker.TimeoutException e) {
Add an explanatory comment about the timeout.