diff --git a/backup/util/xml/tests/writer_test.php b/backup/util/xml/tests/writer_test.php
index 947d825fac3..f7533744643 100644
--- a/backup/util/xml/tests/writer_test.php
+++ b/backup/util/xml/tests/writer_test.php
@@ -282,6 +282,24 @@ final class writer_test extends \basic_testcase {
         $result = $xo->get_allcontents();
         $this->assertEquals($result, '<tagname attrname="attrvalue" /><tagname2 attrname="attrvalue">testsomecontent</tagname2>');
 
+        // Test nullcontent reset.
+        $xo = new memory_xml_output();
+        $xw = new mock_xml_writer($xo);
+        $xw->set_prologue('');
+        $xw->start();
+        $xw->full_tag('tagname', null);
+        $xw->begin_tag('tagname2');
+        $xw->full_tag('tagname3', 'somecontent');
+        $xw->end_tag('tagname2');
+        $xw->stop();
+        $result = $xo->get_allcontents();
+        $expected = <<<XML
+        <tagname /><tagname2>
+          <tagname3>somecontent</tagname3>
+        </tagname2>
+        XML;
+        $this->assertEquals($expected, $result);
+
         // Build a complex XML file and test results against stored file in fixtures
         $xo = new memory_xml_output();
         $xw = new mock_xml_writer($xo);
diff --git a/backup/util/xml/xml_writer.class.php b/backup/util/xml/xml_writer.class.php
index da4ed9ebbf2..35be10db1fd 100644
--- a/backup/util/xml/xml_writer.class.php
+++ b/backup/util/xml/xml_writer.class.php
@@ -216,6 +216,7 @@ class xml_writer {
             $this->lastwastext = true;
             $this->end_tag($tag);
         }
+        $this->nullcontent = false; // Reset nullcontent flag.
     }