diff --git a/src/common/Str.php b/src/common/Str.php
index c454a279..19ebaec3 100644
--- a/src/common/Str.php
+++ b/src/common/Str.php
@@ -21,12 +21,12 @@
 use Error;
 use Nette\Utils\Strings;
 use UConverter;
-use function ord;
 use const MB_CASE_TITLE;
 use function array_keys;
 use function array_pop;
 use function array_shift;
 use function array_values;
+use function chr;
 use function class_exists;
 use function count;
 use function error_clear_last;
@@ -42,6 +42,7 @@
 use function mb_strtoupper;
 use function mb_substr;
 use function min;
+use function ord;
 use function range;
 use function str_replace;
 use function strcasecmp;
@@ -76,7 +77,25 @@ public static function fixEncoding(string $string): string
 
     public static function chr(int $code): string
     {
-        return Strings::chr($code);
+        if ($code < 0 || ($code >= 0xD800 && $code <= 0xDFFF) || $code > 0x10FFFF) {
+            throw new InvalidValueException($code, 'unicode codepoint in range 0x00 to 0xD7FF or 0xE000 to 0x10FFFF');
+        }
+
+        if ($code <= 0x7F) {
+            return chr($code); // 0-7,0-F
+        } elseif ($code <= 0x7FF) {
+            return chr(0b11000000 + ($code >> 6)) // 0xC-D,0-F,8-B,0-9
+                . chr(128 + ($code & 63));
+        } elseif ($code <= 0xFFFF) {
+            return chr(0b11100000 + ($code >> 12)) // 0xE,0-F,8-B,0-9,8-B,0-9
+                . chr(128 + (($code >> 6) & 63))
+                . chr(128 + ($code & 63));
+        } else {
+            return chr(0b11110000 + ($code >> 18)) // 0xF,0-7,8-B,0-9,8-B,0-9,8-B,0-9
+                . chr(128 + (($code >> 12) & 63))
+                . chr(128 + (($code >> 6) & 63))
+                . chr(128 + ($code & 63));
+        }
     }
 
     public static function ord(string $ch): int
diff --git a/tests/src/common/Str.phpt b/tests/src/common/Str.phpt
index f37f38c6..768fd088 100644
--- a/tests/src/common/Str.phpt
+++ b/tests/src/common/Str.phpt
@@ -2,11 +2,46 @@
 
 namespace Dogma\Tests\Str;
 
+use Dogma\InvalidValueException;
 use Dogma\Str;
 use Dogma\Tester\Assert;
 
 require_once __DIR__ . '/../bootstrap.php';
 
+chr:
+Assert::same(Str::chr(0x000000), "\x00");
+Assert::same(Str::chr(0x00007F), "\x7F");
+Assert::same(Str::chr(0x000080), "\u{80}");
+Assert::same(Str::chr(0x0007FF), "\u{7FF}");
+Assert::same(Str::chr(0x000800), "\u{800}");
+Assert::same(Str::chr(0x00D7FF), "\u{D7FF}");
+Assert::same(Str::chr(0x00E000), "\u{E000}");
+Assert::same(Str::chr(0x00FFFF), "\u{FFFF}");
+Assert::same(Str::chr(0x010000), "\u{10000}");
+Assert::same(Str::chr(0x10FFFF), "\u{10FFFF}");
+
+foreach ([-1, 0xD800, 0xDFFF, 0x110000] as $code) {
+    Assert::exception(
+        static function() use ($code): void {
+            Str::chr($code);
+        },
+        InvalidValueException::class
+    );
+}
+
+
+ord:
+Assert::same(Str::ord("\x00"), 0x000000);
+Assert::same(Str::ord("\x7F"), 0x00007F);
+Assert::same(Str::ord("\u{80}"), 0x000080);
+Assert::same(Str::ord("\u{7FF}"), 0x0007FF);
+Assert::same(Str::ord("\u{800}"), 0x000800);
+Assert::same(Str::ord("\u{D7FF}"), 0x00D7FF);
+Assert::same(Str::ord("\u{E000}"), 0x00E000);
+Assert::same(Str::ord("\u{FFFF}"), 0x00FFFF);
+Assert::same(Str::ord("\u{10000}"), 0x010000);
+Assert::same(Str::ord("\u{10FFFF}"), 0x10FFFF);
+
 
 between:
 Assert::same(Str::between('abc@def#ghi', '@', '#'), 'def');