diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 6beda0fda1..7bd365ecb7 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -4,6 +4,7 @@ Yii Framework 2 Change Log
 2.0.16 under development
 ------------------------
 
+- Bug #16974: Regular Expression Validator to include support for 'u' (UTF-8) modifier (Dzhuneyt)
 - Chg #16941: Set `yii\console\controllers\MigrateController::useTablePrefix` to true as default value (GHopperMSK)
 - Bug #16966: Fix ArrayExpression support in related tables (GHopperMSK)
 - Bug #16891: Fixed Pagination::totalCount initialized incorrectly (taobig)
diff --git a/framework/helpers/BaseHtml.php b/framework/helpers/BaseHtml.php
index 5b0440b291..46987a359a 100644
--- a/framework/helpers/BaseHtml.php
+++ b/framework/helpers/BaseHtml.php
@@ -2318,7 +2318,7 @@ class BaseHtml
             $pattern = substr($pattern, 0, $pos + 1);
         }
         if (!empty($flag)) {
-            $pattern .= preg_replace('/[^igm]/', '', $flag);
+            $pattern .= preg_replace('/[^igmu]/', '', $flag);
         }
 
         return $pattern;
diff --git a/tests/framework/helpers/HtmlTest.php b/tests/framework/helpers/HtmlTest.php
index 8e1846e10a..950a8c348b 100644
--- a/tests/framework/helpers/HtmlTest.php
+++ b/tests/framework/helpers/HtmlTest.php
@@ -1800,6 +1800,11 @@ EOD;
         $expected = '/([a-z0-9-]+)/gim';
         $actual = Html::escapeJsRegularExpression('/([a-z0-9-]+)/Ugimex');
         $this->assertSame($expected, $actual);
+
+        // Make sure that just allowed REGEX modifiers remain after the escaping
+        $expected = '/([a-z0-9-]+)/ugim';
+        $actual = Html::escapeJsRegularExpression('/([a-z0-9-]+)/dugimex');
+        $this->assertSame($expected, $actual);
     }
 
     public function testActiveDropDownList()