diff --git a/question/type/numerical/question.php b/question/type/numerical/question.php
index 8df2ce93486..809eec12f00 100644
--- a/question/type/numerical/question.php
+++ b/question/type/numerical/question.php
@@ -172,7 +172,7 @@ class qtype_numerical_question extends question_graded_automatically {
 
     /**
      * Get an answer that contains the feedback and fraction that should be
-     * awarded for this resonse.
+     * awarded for this response.
      * @param number $value the numerical value of a response.
      * @param number $multiplier for the unit the student gave, if any. When no
      *      unit was given, or an unrecognised unit was given, $multiplier will be null.
@@ -188,7 +188,7 @@ class qtype_numerical_question extends question_graded_automatically {
         } else {
             $scaledvalue = $value;
         }
-        foreach ($this->answers as $aid => $answer) {
+        foreach ($this->answers as $answer) {
             if ($answer->within_tolerance($scaledvalue)) {
                 $answer->unitisright = !is_null($multiplier);
                 return $answer;
@@ -266,7 +266,11 @@ class qtype_numerical_question extends question_graded_automatically {
             $resp = $this->ap->add_unit($resp, $unit);
         }
 
-        if (!$ans) {
+        if ($value === null) {
+            // Invalid response shown as no response (but show actual response).
+            return array($this->id => new question_classified_response(null, $resp, 0));
+        } else if (!$ans) {
+            // Does not match any answer.
             return array($this->id => new question_classified_response(0, $resp, 0));
         }
 
diff --git a/question/type/numerical/tests/question_test.php b/question/type/numerical/tests/question_test.php
index 84fc7d0d7c4..73a69605b8d 100644
--- a/question/type/numerical/tests/question_test.php
+++ b/question/type/numerical/tests/question_test.php
@@ -214,9 +214,10 @@ class qtype_numerical_question_test extends advanced_testcase {
         $this->assertEquals(array(
                 new question_classified_response(13, '3.14', 1.0)),
                 $num->classify_response(array('answer' => '3.14')));
+        // Invalid response.
         $this->assertEquals(array(
-                question_classified_response::no_response()),
-                $num->classify_response(array('answer' => '')));
+                new question_classified_response(null, 'abc', 0.0)),
+                $num->classify_response(array('answer' => 'abc')));
     }
 
     public function test_classify_response_no_star() {
@@ -230,9 +231,10 @@ class qtype_numerical_question_test extends advanced_testcase {
         $this->assertEquals(array(
                 new question_classified_response(0, '42', 0.0)),
                 $num->classify_response(array('answer' => '42')));
+        // Invalid response.
         $this->assertEquals(array(
-                question_classified_response::no_response()),
-                $num->classify_response(array('answer' => '')));
+                new question_classified_response(null, 'abc', 0.0)),
+                $num->classify_response(array('answer' => 'abc')));
     }
 
     public function test_classify_response_unit() {
@@ -260,6 +262,10 @@ class qtype_numerical_question_test extends advanced_testcase {
         $this->assertEquals(array(
                 question_classified_response::no_response()),
                 $num->classify_response(array('answer' => '')));
+        // Invalid response.
+        $this->assertEquals(array(
+                new question_classified_response(null, 'abc m', 0.0)),
+                $num->classify_response(array('answer' => 'abc', 'unit' => 'm')));
     }
 
     public function test_classify_response_unit_no_star() {
@@ -279,6 +285,10 @@ class qtype_numerical_question_test extends advanced_testcase {
         $this->assertEquals(array(
                 question_classified_response::no_response()),
                 $num->classify_response(array('answer' => '', 'unit' => '')));
+        // Invalid response.
+        $this->assertEquals(array(
+                            new question_classified_response(null, 'abc m', 0.0)),
+                            $num->classify_response(array('answer' => 'abc', 'unit' => 'm')));
     }
 
     public function test_classify_response_currency() {
@@ -291,5 +301,9 @@ class qtype_numerical_question_test extends advanced_testcase {
         $this->assertEquals(array(
                 new question_classified_response(13, '1 332', 0.8)),
                 $num->classify_response(array('answer' => '1 332')));
+        // Invalid response.
+        $this->assertEquals(array(
+                new question_classified_response(null, '$abc', 0.0)),
+                $num->classify_response(array('answer' => '$abc')));
     }
-}
\ No newline at end of file
+}