diff --git a/src/Mbstring/Mbstring.php b/src/Mbstring/Mbstring.php
index 3d45c9d9a..31e36a368 100644
--- a/src/Mbstring/Mbstring.php
+++ b/src/Mbstring/Mbstring.php
@@ -983,7 +983,7 @@ public static function mb_ltrim(string $string, ?string $characters = null, ?str
 
     public static function mb_rtrim(string $string, ?string $characters = null, ?string $encoding = null): string
     {
-        return self::mb_internal_trim('{[%s]+$}D', $string, $characters, $encoding, __FUNCTION__);
+        return self::mb_internal_trim('{[%s]+$}Du', $string, $characters, $encoding, __FUNCTION__);
     }
 
     private static function mb_internal_trim(string $regex, string $string, ?string $characters, ?string $encoding, string $function): string
diff --git a/tests/Mbstring/MbstringTest.php b/tests/Mbstring/MbstringTest.php
index 2020f4566..49a9aff10 100644
--- a/tests/Mbstring/MbstringTest.php
+++ b/tests/Mbstring/MbstringTest.php
@@ -886,6 +886,7 @@ public static function mbLTrimProvider(): iterable
         yield [' test ', ' test ', ''];
 
         yield ['いああああ', 'あああああああああああああああああああああああああああああああああいああああ', 'あ'];
+        yield ['あいうえお　', '　あいうえお　'];
 
         yield ['漢字', "\u{FFFE}漢字", "\u{FFFE}\u{FEFF}"];
         yield [' abcd ', ' abcd ', ''];
@@ -902,6 +903,7 @@ public static function mbRTrimProvider(): iterable
         yield ['                                                                                                                                 a', str_repeat(' ', 129).'a'];
 
         yield ['あああああああああああああああああああああああああああああああああい', 'あああああああああああああああああああああああああああああああああいああああ', 'あ'];
+        yield ['　あいうえお', '　あいうえお　'];
 
         yield [' abcd ', ' abcd ', ''];