diff --git a/lib/setup.php b/lib/setup.php
index ccb2b58bbe8..6463e5db22a 100644
--- a/lib/setup.php
+++ b/lib/setup.php
@@ -827,6 +827,8 @@ if (empty($CFG->sessiontimeoutwarning)) {
     $CFG->sessiontimeoutwarning = 20 * 60;
 }
 \core\session\manager::start();
+// Prevent ignoresesskey hack from getting carried over to a next page.
+unset($USER->ignoresesskey);
 
 // Set default content type and encoding, developers are still required to use
 // echo $OUTPUT->header() everywhere, anything that gets set later should override these headers.