diff --git a/mod/workshop/backup/moodle2/restore_workshop_stepslib.php b/mod/workshop/backup/moodle2/restore_workshop_stepslib.php
index 7a2a5aee297..3b414e8fcfc 100644
--- a/mod/workshop/backup/moodle2/restore_workshop_stepslib.php
+++ b/mod/workshop/backup/moodle2/restore_workshop_stepslib.php
@@ -104,6 +104,9 @@ class restore_workshop_activity_structure_step extends restore_activity_structur
         $oldid = $data->id;
         $data->course = $this->get_courseid();
 
+        $data->strategy = clean_param($data->strategy, PARAM_PLUGIN);
+        $data->evaluation = clean_param($data->evaluation, PARAM_PLUGIN);
+
         // Any changes to the list of dates that needs to be rolled should be same during course restore and course reset.
         // See MDL-9367.
         $data->submissionstart = $this->apply_date_offset($data->submissionstart);
diff --git a/mod/workshop/locallib.php b/mod/workshop/locallib.php
index 7e8e5b2f66e..13449ea1d64 100644
--- a/mod/workshop/locallib.php
+++ b/mod/workshop/locallib.php
@@ -215,6 +215,10 @@ class workshop {
                 $this->{$field} = $value;
             }
         }
+
+        $this->strategy = clean_param($this->strategy, PARAM_PLUGIN);
+        $this->evaluation = clean_param($this->evaluation, PARAM_PLUGIN);
+
         if (is_null($cm) || is_null($course)) {
             throw new coding_exception('Must specify $cm and $course');
         }
@@ -1556,6 +1560,9 @@ class workshop {
         global $CFG;    // because we require other libs here
 
         if (is_null($this->strategyinstance)) {
+            if (empty($this->strategy)) {
+                throw new coding_exception('Unknown grading strategy');
+            }
             $strategylib = __DIR__ . '/form/' . $this->strategy . '/lib.php';
             if (is_readable($strategylib)) {
                 require_once($strategylib);
@@ -1581,6 +1588,7 @@ class workshop {
     public function set_grading_evaluation_method($method) {
         global $DB;
 
+        $method = clean_param($method, PARAM_PLUGIN);
         $evaluationlib = __DIR__ . '/eval/' . $method . '/lib.php';
 
         if (is_readable($evaluationlib)) {