diff --git a/lib/pear/HTML/QuickForm/Rule/Range.php b/lib/pear/HTML/QuickForm/Rule/Range.php
index 67a11802e39..e2db391cbd1 100644
--- a/lib/pear/HTML/QuickForm/Rule/Range.php
+++ b/lib/pear/HTML/QuickForm/Rule/Range.php
@@ -36,7 +36,7 @@ class HTML_QuickForm_Rule_Range extends HTML_QuickForm_Rule
      */
     function validate($value, $options = null)
     {
-        $length = strlen($value);
+        $length = core_text::strlen($value);
         switch ($this->name) {
             case 'minlength': return ($length >= $options);
             case 'maxlength': return ($length <= $options);
@@ -61,4 +61,4 @@ class HTML_QuickForm_Rule_Range extends HTML_QuickForm_Rule
     } // end func getValidationScript
 
 } // end class HTML_QuickForm_Rule_Range
-?>
\ No newline at end of file
+?>
diff --git a/lib/pear/README_MOODLE.txt b/lib/pear/README_MOODLE.txt
index e97f631e8a0..537071def41 100644
--- a/lib/pear/README_MOODLE.txt
+++ b/lib/pear/README_MOODLE.txt
@@ -20,4 +20,4 @@ Full of our custom hacks, no way to upgrade to latest upstream.
 Most probably we will stop using this library in the future.
 
 MDL-20876 - replaced split() with explode() or preg_split() where appropriate
-
+MDL-40267 - Moodle core_text strlen functions used for range rule rule to be utf8 safe.
diff --git a/lib/tests/formslib_test.php b/lib/tests/formslib_test.php
index e368c647b74..1ad2776bd31 100644
--- a/lib/tests/formslib_test.php
+++ b/lib/tests/formslib_test.php
@@ -121,6 +121,89 @@ class core_formslib_testcase extends advanced_testcase {
         }
     }
 
+    public function test_range_rule() {
+        global $CFG;
+
+        require_once('HTML/QuickForm/Rule/Range.php'); // Requires this pear stuff.
+
+        $strictformsrequired = null;
+        if (isset($CFG->strictformsrequired)) {
+            $strictformsrequired = $CFG->strictformsrequired;
+        }
+
+        $rule = new HTML_QuickForm_Rule_Range();
+
+        // First run the tests with strictformsrequired off.
+        $CFG->strictformsrequired = false;
+        // Passes.
+        $rule->setName('minlength'); // Let's verify some min lengths.
+        $this->assertTrue($rule->validate('12', 2));
+        $this->assertTrue($rule->validate('123', 2));
+        $this->assertTrue($rule->validate('áé', 2));
+        $this->assertTrue($rule->validate('áéí', 2));
+        $rule->setName('maxlength'); // Let's verify some max lengths.
+        $this->assertTrue($rule->validate('1', 2));
+        $this->assertTrue($rule->validate('12', 2));
+        $this->assertTrue($rule->validate('á', 2));
+        $this->assertTrue($rule->validate('áé', 2));
+        $rule->setName('----'); // Let's verify some ranges.
+        $this->assertTrue($rule->validate('', array(0, 2)));
+        $this->assertTrue($rule->validate('1', array(0, 2)));
+        $this->assertTrue($rule->validate('12', array(0, 2)));
+        $this->assertTrue($rule->validate('á', array(0, 2)));
+        $this->assertTrue($rule->validate('áé', array(0, 2)));
+
+        // Fail.
+        $rule->setName('minlength'); // Let's verify some min lengths.
+        $this->assertFalse($rule->validate('', 2));
+        $this->assertFalse($rule->validate('1', 2));
+        $this->assertFalse($rule->validate('á', 2));
+        $rule->setName('maxlength'); // Let's verify some max lengths.
+        $this->assertFalse($rule->validate('123', 2));
+        $this->assertFalse($rule->validate('áéí', 2));
+        $rule->setName('----'); // Let's verify some ranges.
+        $this->assertFalse($rule->validate('', array(1, 2)));
+        $this->assertFalse($rule->validate('123', array(1, 2)));
+        $this->assertFalse($rule->validate('áéí', array(1, 2)));
+
+        // Now run the same tests with it on to make sure things work as expected.
+        $CFG->strictformsrequired = true;
+        // Passes.
+        $rule->setName('minlength'); // Let's verify some min lengths.
+        $this->assertTrue($rule->validate('12', 2));
+        $this->assertTrue($rule->validate('123', 2));
+        $this->assertTrue($rule->validate('áé', 2));
+        $this->assertTrue($rule->validate('áéí', 2));
+        $rule->setName('maxlength'); // Let's verify some min lengths.
+        $this->assertTrue($rule->validate('1', 2));
+        $this->assertTrue($rule->validate('12', 2));
+        $this->assertTrue($rule->validate('á', 2));
+        $this->assertTrue($rule->validate('áé', 2));
+        $rule->setName('----'); // Let's verify some ranges.
+        $this->assertTrue($rule->validate('', array(0, 2)));
+        $this->assertTrue($rule->validate('1', array(0, 2)));
+        $this->assertTrue($rule->validate('12', array(0, 2)));
+        $this->assertTrue($rule->validate('á', array(0, 2)));
+        $this->assertTrue($rule->validate('áé', array(0, 2)));
+
+        // Fail.
+        $rule->setName('minlength'); // Let's verify some min lengths.
+        $this->assertFalse($rule->validate('', 2));
+        $this->assertFalse($rule->validate('1', 2));
+        $this->assertFalse($rule->validate('á', 2));
+        $rule->setName('maxlength'); // Let's verify some min lengths.
+        $this->assertFalse($rule->validate('123', 2));
+        $this->assertFalse($rule->validate('áéí', 2));
+        $rule->setName('----'); // Let's verify some ranges.
+        $this->assertFalse($rule->validate('', array(1, 2)));
+        $this->assertFalse($rule->validate('123', array(1, 2)));
+        $this->assertFalse($rule->validate('áéí', array(1, 2)));
+
+        if (isset($strictformsrequired)) {
+            $CFG->strictformsrequired = $strictformsrequired;
+        }
+    }
+
     public function test_generate_id_select() {
         $el = new MoodleQuickForm_select('choose_one', 'Choose one',
             array(1 => 'One', '2' => 'Two'));