diff --git a/admin/user.php b/admin/user.php
index e857cca0593..876d986f7c3 100644
--- a/admin/user.php
+++ b/admin/user.php
@@ -62,12 +62,12 @@
 
         $USER = $user;
         $USER->loggedin = true;
-        $USER->sesskey  = random_string(10); // for added security, used to check script parameters
         $USER->sessionIP = md5(getremoteaddr());   // Store the current IP in the session
         $USER->site = $CFG->wwwroot;
         $USER->admin = true;
         $USER->teacher["$site->id"] = true;
         $USER->newadminuser = true;
+        set_user_sesskey(); // for added security, used to check script parameters
 
         redirect("$CFG->wwwroot/user/edit.php?id=$user->id&course=$site->id");
         exit;
diff --git a/blocks/admin/block_admin.php b/blocks/admin/block_admin.php
index cb9747cde2c..87e25480a94 100644
--- a/blocks/admin/block_admin.php
+++ b/blocks/admin/block_admin.php
@@ -48,7 +48,7 @@ class block_admin extends block_base {
         }
 
         if (iscreator()) {
-            $this->content->items[] = '<a href="'.$CFG->wwwroot.'/course/index.php?edit=on&amp;sesskey='.$USER->sesskey.'">'.get_string('courses').'</a>';
+            $this->content->items[] = '<a href="'.$CFG->wwwroot.'/course/index.php?edit=on&amp;sesskey='.set_user_sesskey().'">'.get_string('courses').'</a>';
             $this->content->icons[] = '<img src="'.$CFG->pixpath.'/i/course.gif" height="16" width="16" alt="" />';
         }
 
diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index 78966e09551..9a7b27a809e 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -793,6 +793,23 @@ function get_user_timezone($tz = 99) {
 
 /// USER AUTHENTICATION AND LOGIN ////////////////////////////////////////
 
+// Makes sure that $USER->sesskey exists, if $USER itself exists. It sets a new sesskey
+// if one does not already exist, but does not overwrite existing sesskeys. Returns the
+// sesskey string if $USER exists, or boolean false if not.
+function set_user_sesskey() {
+    global $USER;
+
+    if(!isset($USER)) {
+        return false;
+    }
+
+    if (empty($USER->sesskey)) {
+        $USER->sesskey = random_string(10);
+    }
+
+    return $USER->sesskey;
+}
+
 /**
  * This function checks that the current user is logged in, and optionally
  * whether they are "logged in" or allowed to be in a particular course.
@@ -863,9 +880,7 @@ function require_login($courseid=0, $autologinguest=true) {
     }
 
     // Make sure the USER has a sesskey set up.  Used for checking script parameters.
-    if (empty($USER->sesskey)) {
-        $USER->sesskey = random_string(10);
-    }
+    set_user_sesskey();
 
     // Check that the user has agreed to a site policy if there is one
     if (!empty($CFG->sitepolicy)) {
diff --git a/login/index.php b/login/index.php
index 0a1c4ab106a..b35ba4e7923 100644
--- a/login/index.php
+++ b/login/index.php
@@ -78,12 +78,12 @@
 
             $USER = $user;
             if (!empty($USER->description)) {
-                $USER->description = true;       // No need to cart all of it around
+                $USER->description = true;   // No need to cart all of it around
             }
             $USER->loggedin = true;
-            $USER->site     = $CFG->wwwroot;     // for added security, store the site in the session
-            $USER->sesskey  = random_string(10); // for added security, used to check script parameters
-            
+            $USER->site     = $CFG->wwwroot; // for added security, store the site in the session
+            set_user_sesskey();              // for added security, used to check script parameters
+
             if ($USER->username == "guest") {
                 $USER->lang       = $CFG->lang;               // Guest language always same as site
                 $USER->firstname  = get_string("guestuser");  // Name always in current language