diff --git a/backup/moodle2/backup_stepslib.php b/backup/moodle2/backup_stepslib.php
index 436f19f36dd..9a32da1531e 100644
--- a/backup/moodle2/backup_stepslib.php
+++ b/backup/moodle2/backup_stepslib.php
@@ -930,8 +930,11 @@ class backup_gradebook_structure_step extends backup_structure_step {
         $grade_setting = new backup_nested_element('grade_setting', 'id', array(
             'name', 'value'));
 
+        $gradebook_attributes = new backup_nested_element('attributes', null, array('calculations_freeze'));
 
         // Build the tree
+        $gradebook->add_child($gradebook_attributes);
+
         $gradebook->add_child($grade_categories);
         $grade_categories->add_child($grade_category);
 
@@ -946,14 +949,15 @@ class backup_gradebook_structure_step extends backup_structure_step {
         $gradebook->add_child($grade_settings);
         $grade_settings->add_child($grade_setting);
 
+        // Define sources
+
         // Add attribute with gradebook calculation freeze date if needed.
+        $attributes = new stdClass();
         $gradebookcalculationfreeze = get_config('core', 'gradebook_calculations_freeze_' . $this->get_courseid());
         if ($gradebookcalculationfreeze) {
-            $gradebook->add_attributes(array('calculations_freeze'));
-            $gradebook->get_attribute('calculations_freeze')->set_value($gradebookcalculationfreeze);
+            $attributes->calculations_freeze = $gradebookcalculationfreeze;
         }
-
-        // Define sources
+        $gradebook_attributes->set_source_array([$attributes]);
 
         //Include manual, category and the course grade item
         $grade_items_sql ="SELECT * FROM {grade_items}
diff --git a/backup/moodle2/restore_stepslib.php b/backup/moodle2/restore_stepslib.php
index dfe5cea30e3..3473004f9ac 100644
--- a/backup/moodle2/restore_stepslib.php
+++ b/backup/moodle2/restore_stepslib.php
@@ -121,6 +121,21 @@ class restore_gradebook_structure_step extends restore_structure_step {
             return false;
         }
 
+        // Identify the backup we're dealing with.
+        $backuprelease = floatval($this->get_task()->get_info()->backup_release); // The major version: 2.9, 3.0, ...
+        $backupbuild = 0;
+        preg_match('/(\d{8})/', $this->get_task()->get_info()->moodle_release, $matches);
+        if (!empty($matches[1])) {
+            $backupbuild = (int) $matches[1]; // The date of Moodle build at the time of the backup.
+        }
+
+        // On older versions the freeze value has to be converted.
+        // We do this from here as it is happening right before the file is read.
+        // This only targets the backup files that can contain the legacy freeze.
+        if ($backupbuild > 20150618 && ($backuprelease < 3.0 || $backupbuild < 20160527)) {
+            $this->rewrite_step_backup_file_for_legacy_freeze($fullpath);
+        }
+
         // Arrived here, execute the step
         return true;
      }
@@ -129,7 +144,7 @@ class restore_gradebook_structure_step extends restore_structure_step {
         $paths = array();
         $userinfo = $this->task->get_setting_value('users');
 
-        $paths[] = new restore_path_element('gradebook', '/gradebook');
+        $paths[] = new restore_path_element('attributes', '/gradebook/attributes');
         $paths[] = new restore_path_element('grade_category', '/gradebook/grade_categories/grade_category');
         $paths[] = new restore_path_element('grade_item', '/gradebook/grade_items/grade_item');
         if ($userinfo) {
@@ -141,7 +156,7 @@ class restore_gradebook_structure_step extends restore_structure_step {
         return $paths;
     }
 
-    protected function process_gradebook($data) {
+    protected function process_attributes($data) {
         // For non-merge restore types:
         // Unset 'gradebook_calculations_freeze_' in the course and replace with the one from the backup.
         $target = $this->get_task()->get_target();
@@ -581,6 +596,85 @@ class restore_gradebook_structure_step extends restore_structure_step {
             }
         }
     }
+
+    /**
+     * Rewrite step definition to handle the legacy freeze attribute.
+     *
+     * In previous backups the calculations_freeze property was stored as an attribute of the
+     * top level node <gradebook>. The backup API, however, do not process grandparent nodes.
+     * It only processes definitive children, and their parent attributes.
+     *
+     * We had:
+     *
+     * <gradebook calculations_freeze="20160511">
+     *   <grade_categories>
+     *     <grade_category id="10">
+     *       <depth>1</depth>
+     *       ...
+     *     </grade_category>
+     *   </grade_categories>
+     *   ...
+     * </gradebook>
+     *
+     * And this method will convert it to:
+     *
+     * <gradebook >
+     *   <attributes>
+     *     <calculations_freeze>20160511</calculations_freeze>
+     *   </attributes>
+     *   <grade_categories>
+     *     <grade_category id="10">
+     *       <depth>1</depth>
+     *       ...
+     *     </grade_category>
+     *   </grade_categories>
+     *   ...
+     * </gradebook>
+     *
+     * Note that we cannot just load the XML file in memory as it could potentially be huge.
+     * We can also completely ignore if the node <attributes> is already in the backup
+     * file as it never existed before.
+     *
+     * @param string $filepath The absolute path to the XML file.
+     * @return void
+     */
+    protected function rewrite_step_backup_file_for_legacy_freeze($filepath) {
+        $foundnode = false;
+        $newfile = make_request_directory(true) . DIRECTORY_SEPARATOR . 'file.xml';
+        $fr = fopen($filepath, 'r');
+        $fw = fopen($newfile, 'w');
+        if ($fr && $fw) {
+            while (($line = fgets($fr, 4096)) !== false) {
+                if (!$foundnode && strpos($line, '<gradebook ') === 0) {
+                    $foundnode = true;
+                    $matches = array();
+                    $pattern = '@calculations_freeze=.([0-9]+).@';
+                    if (preg_match($pattern, $line, $matches)) {
+                        $freeze = $matches[1];
+                        $line = preg_replace($pattern, '', $line);
+                        $line .= "  <attributes>\n    <calculations_freeze>$freeze</calculations_freeze>\n  </attributes>\n";
+                    }
+                }
+                fputs($fw, $line);
+            }
+            if (!feof($fr)) {
+                throw new restore_step_exception('Error while attempting to rewrite the gradebook step file.');
+            }
+            fclose($fr);
+            fclose($fw);
+            if (!rename($newfile, $filepath)) {
+                throw new restore_step_exception('Error while attempting to rename the gradebook step file.');
+            }
+        } else {
+            if ($fr) {
+                fclose($fr);
+            }
+            if ($fw) {
+                fclose($fw);
+            }
+        }
+    }
+
 }
 
 /**
diff --git a/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/1.expectation b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/1.expectation
new file mode 100644
index 00000000000..99e8d85db0d
--- /dev/null
+++ b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/1.expectation
@@ -0,0 +1,10 @@
+<gradebook >
+  <attributes>
+    <calculations_freeze>20160511</calculations_freeze>
+  </attributes>
+  <grade_categories>
+    <grade_category id="10">
+      <depth>1</depth>
+    </grade_category>
+  </grade_categories>
+</gradebook>
diff --git a/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/1.test b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/1.test
new file mode 100644
index 00000000000..830eca68bc9
--- /dev/null
+++ b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/1.test
@@ -0,0 +1,7 @@
+<gradebook calculations_freeze="20160511">
+  <grade_categories>
+    <grade_category id="10">
+      <depth>1</depth>
+    </grade_category>
+  </grade_categories>
+</gradebook>
diff --git a/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/2.expectation b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/2.expectation
new file mode 100644
index 00000000000..b4f21d48205
--- /dev/null
+++ b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/2.expectation
@@ -0,0 +1,10 @@
+<gradebook some_other_value="false" >
+  <attributes>
+    <calculations_freeze>20160511</calculations_freeze>
+  </attributes>
+  <grade_categories>
+    <grade_category id="10">
+      <depth>1</depth>
+    </grade_category>
+  </grade_categories>
+</gradebook>
diff --git a/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/2.test b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/2.test
new file mode 100644
index 00000000000..04f3b63eef7
--- /dev/null
+++ b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/2.test
@@ -0,0 +1,7 @@
+<gradebook some_other_value="false" calculations_freeze="20160511">
+  <grade_categories>
+    <grade_category id="10">
+      <depth>1</depth>
+    </grade_category>
+  </grade_categories>
+</gradebook>
diff --git a/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/3.expectation b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/3.expectation
new file mode 100644
index 00000000000..c61f19d99a3
--- /dev/null
+++ b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/3.expectation
@@ -0,0 +1,10 @@
+<gradebook some_other_value="false"  and_another_value="42">
+  <attributes>
+    <calculations_freeze>20160511</calculations_freeze>
+  </attributes>
+  <grade_categories>
+    <grade_category id="10">
+      <depth>1</depth>
+    </grade_category>
+  </grade_categories>
+</gradebook>
diff --git a/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/3.test b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/3.test
new file mode 100644
index 00000000000..39c46bc57c6
--- /dev/null
+++ b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/3.test
@@ -0,0 +1,7 @@
+<gradebook some_other_value="false" calculations_freeze="20160511" and_another_value="42">
+  <grade_categories>
+    <grade_category id="10">
+      <depth>1</depth>
+    </grade_category>
+  </grade_categories>
+</gradebook>
diff --git a/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/4.expectation b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/4.expectation
new file mode 100644
index 00000000000..71070aa82e3
--- /dev/null
+++ b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/4.expectation
@@ -0,0 +1,7 @@
+<gradebookplugin some_other_value="false" calculations_freeze="20160511" and_another_value="42">
+  <grade_categories>
+    <grade_category id="10">
+      <depth>1</depth>
+    </grade_category>
+  </grade_categories>
+</gradebookplugin>
diff --git a/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/4.test b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/4.test
new file mode 100644
index 00000000000..71070aa82e3
--- /dev/null
+++ b/backup/moodle2/tests/fixtures/rewrite_step_backup_file_for_legacy_freeze/4.test
@@ -0,0 +1,7 @@
+<gradebookplugin some_other_value="false" calculations_freeze="20160511" and_another_value="42">
+  <grade_categories>
+    <grade_category id="10">
+      <depth>1</depth>
+    </grade_category>
+  </grade_categories>
+</gradebookplugin>
diff --git a/backup/moodle2/tests/restore_gradebook_structure_step_test.php b/backup/moodle2/tests/restore_gradebook_structure_step_test.php
new file mode 100644
index 00000000000..26856de9597
--- /dev/null
+++ b/backup/moodle2/tests/restore_gradebook_structure_step_test.php
@@ -0,0 +1,92 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Test for restore_stepslib.
+ *
+ * @package core_backup
+ * @copyright 2016 Andrew Nicols <andrew@nicols.co.uk>
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+global $CFG;
+require_once($CFG->dirroot . '/backup/util/includes/backup_includes.php');
+require_once($CFG->dirroot . '/backup/util/includes/restore_includes.php');
+require_once($CFG->libdir . '/completionlib.php');
+
+/**
+ * Test for restore_stepslib.
+ *
+ * @package core_backup
+ * @copyright 2016 Andrew Nicols <andrew@nicols.co.uk>
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class core_backup_restore_gradebook_structure_step_testcase extends advanced_testcase {
+
+    /**
+     * Provide tests for rewrite_step_backup_file_for_legacy_freeze based upon fixtures.
+     *
+     * @return array
+     */
+    public function rewrite_step_backup_file_for_legacy_freeze_provider() {
+        $fixturesdir = realpath(__DIR__ . '/fixtures/rewrite_step_backup_file_for_legacy_freeze/');
+        $tests = [];
+        $iterator = new \RecursiveIteratorIterator(
+                new \RecursiveDirectoryIterator($fixturesdir),
+                \RecursiveIteratorIterator::LEAVES_ONLY);
+
+        foreach ($iterator as $sourcefile) {
+            $pattern = '/\.test$/';
+            if (!preg_match($pattern, $sourcefile)) {
+                continue;
+            }
+
+            $expectfile = preg_replace($pattern, '.expectation', $sourcefile);
+            $test = array($sourcefile, $expectfile);
+            $tests[basename($sourcefile)] = $test;
+        }
+
+        return $tests;
+    }
+
+    /**
+     * @dataProvider rewrite_step_backup_file_for_legacy_freeze_provider
+     * @param   string  $source     The source file to test
+     * @param   string  $expected   The expected result of the transformation
+     */
+    public function test_rewrite_step_backup_file_for_legacy_freeze($source, $expected) {
+        $restore = $this->getMockBuilder('\restore_gradebook_structure_step')
+            ->setMethods(null)
+            ->disableOriginalConstructor()
+            ->getMock()
+            ;
+
+        // Copy the file somewhere as the rewrite_step_backup_file_for_legacy_freeze will write the file.
+        $dir = make_request_directory(true);
+        $filepath = $dir . DIRECTORY_SEPARATOR . 'file.xml';
+        copy($source, $filepath);
+
+        $rc = new \ReflectionClass('\restore_gradebook_structure_step');
+        $rcm = $rc->getMethod('rewrite_step_backup_file_for_legacy_freeze');
+        $rcm->setAccessible(true);
+        $rcm->invoke($restore, $filepath);
+
+        // Check the result.
+        $this->assertFileEquals($expected, $filepath);
+    }
+}