diff --git a/lib/behat/form_field/behat_form_select.php b/lib/behat/form_field/behat_form_select.php
index 17bc943d7ef..dce4028af8c 100644
--- a/lib/behat/form_field/behat_form_select.php
+++ b/lib/behat/form_field/behat_form_select.php
@@ -104,6 +104,11 @@ class behat_form_select extends behat_form_field {
                 // Wrapped in a try & catch as we can fall into race conditions
                 // and the element may not be there.
                 try {
+
+                    // Wait for all the possible AJAX requests that have been
+                    // already triggered by selectOption() to be finished.
+                    $this->session->wait(behat_base::TIMEOUT * 1000, behat_base::PAGE_READY_JS);
+
                     current($optionnodes)->click();
                 } catch (Exception $e) {
                     // We continue and return as this means that the element is not there or it is not the same.
@@ -112,6 +117,11 @@ class behat_form_select extends behat_form_field {
             }
 
         } else {
+
+            // Wait for all the possible AJAX requests that have been
+            // already triggered by selectOption() to be finished.
+            $this->session->wait(behat_base::TIMEOUT * 1000, behat_base::PAGE_READY_JS);
+
             // Wrapped in a try & catch as we can fall into race conditions
             // and the element may not be there.
             try {
@@ -127,6 +137,10 @@ class behat_form_select extends behat_form_field {
                 return;
             }
 
+            // Wait for all the possible AJAX requests that have been
+            // already triggered by selectOption() to be finished.
+            $this->session->wait(behat_base::TIMEOUT * 1000, behat_base::PAGE_READY_JS);
+
             // Wrapped in a try & catch as we can fall into race conditions
             // and the element may not be there.
             try {
diff --git a/lib/tests/behat/behat_hooks.php b/lib/tests/behat/behat_hooks.php
index e596e5ec43f..69f8b32ed3c 100644
--- a/lib/tests/behat/behat_hooks.php
+++ b/lib/tests/behat/behat_hooks.php
@@ -281,6 +281,7 @@ class behat_hooks extends behat_base {
     /**
      * Waits for all the JS to be loaded.
      *
+     * @throws \Exception
      * @throws NoSuchWindow
      * @throws UnknownError
      * @return bool True or false depending whether all the JS is loaded or not.
@@ -314,9 +315,12 @@ class behat_hooks extends behat_base {
             usleep(100000);
         }
 
-        // Timeout waiting for JS to complete.
-        // TODO MDL-43173 We should fail the scenarios if JS loading times out.
-        return false;
+        // Timeout waiting for JS to complete. It will be catched and forwarded to behat_hooks::i_look_for_exceptions().
+        // It is unlikely that Javascript code of a page or an AJAX request needs more than self::EXTENDED_TIMEOUT seconds
+        // to be loaded, although when pages contains Javascript errors M.util.js_complete() can not be executed, so the
+        // number of JS pending code and JS completed code will not match and we will reach this point.
+        throw new \Exception('Javascript code and/or AJAX requests are not ready after ' . self::EXTENDED_TIMEOUT .
+            ' seconds. There is a Javascript error or the code is extremely slow.');
     }
 
     /**