diff --git a/src/Strings/Multibyte/OmniString.php b/src/Strings/Multibyte/OmniString.php
--- a/src/Strings/Multibyte/OmniString.php
+++ b/src/Strings/Multibyte/OmniString.php
@@ -20,9 +20,9 @@
     /// Constructor
     ///
 
-    public function __construct (string $value = '', ?string $encoding = null) {
+    public function __construct (string $value = '', string $encoding = '') {
         $this->value = $value;
-        $this->setEncoding($encoding ?? "UTF-8");
+        $this->setEncoding($encoding ?: "UTF-8");
     }
 
     ///
diff --git a/src/Strings/Multibyte/StringPad.php b/src/Strings/Multibyte/StringPad.php
--- a/src/Strings/Multibyte/StringPad.php
+++ b/src/Strings/Multibyte/StringPad.php
@@ -56,14 +56,14 @@
         int $padLength = 0,
         string $padString = ' ',
         int $padType = STR_PAD_RIGHT,
-        ?string $encoding = null
+        string $encoding = ''
     ) {
         $this->input = $input;
         $this->padLength = $padLength;
         $this->padString = $padString;
 
         $this->setPadType($padType);
-        $this->setEncoding($encoding ?? mb_internal_encoding());
+        $this->setEncoding($encoding ?: mb_internal_encoding());
     }
 
     ///
diff --git a/src/Strings/Multibyte/StringUtilities.php b/src/Strings/Multibyte/StringUtilities.php
--- a/src/Strings/Multibyte/StringUtilities.php
+++ b/src/Strings/Multibyte/StringUtilities.php
@@ -29,7 +29,7 @@
             ->setPadLength($padLength)
             ->setPadString($padString)
             ->setPadType($padType)
-            ->setEncoding($encoding)
+            ->setEncoding($encoding ?: mb_internal_encoding())
             ->pad();
     }
 
diff --git a/tests/Strings/Multibyte/StringUtilitiesTest.php b/tests/Strings/Multibyte/StringUtilitiesTest.php
--- a/tests/Strings/Multibyte/StringUtilitiesTest.php
+++ b/tests/Strings/Multibyte/StringUtilitiesTest.php
@@ -26,6 +26,12 @@
         $this->assertEquals($expected, $paddedString);
     }
 
+    public function testPadWithDefaultArguments () : void {
+        $this->assertEquals("foo ", StringUtilities::pad("foo", 4));
+        $this->assertEquals("foo_", StringUtilities::pad("foo", 4, '_'));
+        $this->assertEquals("_foo", StringUtilities::pad("foo", 4, '_', STR_PAD_LEFT));
+    }
+
     public function testSupportedEncoding () : void {
         $this->assertTrue(StringUtilities::isSupportedEncoding("UTF-8"));
         $this->assertFalse(StringUtilities::isSupportedEncoding("notexisting"));