diff --git a/question/engine/questionattempt.php b/question/engine/questionattempt.php
index bde5115d062..4a2253ebcef 100644
--- a/question/engine/questionattempt.php
+++ b/question/engine/questionattempt.php
@@ -884,10 +884,10 @@ class question_attempt {
             case self::PARAM_MARK:
                 // Special case to work around PARAM_NUMBER converting '' to 0.
                 $mark = $this->get_submitted_var($name, PARAM_RAW_TRIMMED, $postdata);
-                if ($mark === '') {
+                if ($mark === '' || is_null($mark)) {
                     return $mark;
                 } else {
-                    return $this->get_submitted_var($name, PARAM_NUMBER, $postdata);
+                    return clean_param(str_replace(',', '.', $mark), PARAM_NUMBER);
                 }
 
             case self::PARAM_FILES:
diff --git a/question/engine/simpletest/testquestionattempt.php b/question/engine/simpletest/testquestionattempt.php
index 84a4d4679ad..b4fe736b8b0 100644
--- a/question/engine/simpletest/testquestionattempt.php
+++ b/question/engine/simpletest/testquestionattempt.php
@@ -123,6 +123,16 @@ class question_attempt_test extends UnitTestCase {
                 'name', question_attempt::PARAM_MARK, array('name' => '123')));
     }
 
+    public function test_get_submitted_var_param_mark_number_uk_decimal() {
+        $this->assertIdentical(123.45, $this->qa->get_submitted_var(
+                'name', question_attempt::PARAM_MARK, array('name' => '123.45')));
+    }
+
+    public function test_get_submitted_var_param_mark_number_eu_decimal() {
+        $this->assertIdentical(123.45, $this->qa->get_submitted_var(
+                'name', question_attempt::PARAM_MARK, array('name' => '123,45')));
+    }
+
     public function test_get_submitted_var_param_mark_invalid() {
         $this->assertIdentical(0.0, $this->qa->get_submitted_var(
                 'name', question_attempt::PARAM_MARK, array('name' => 'frog')));