diff --git a/src/CommandLine/Console.php b/src/CommandLine/Console.php
index c2871df..d64f1c3 100644
--- a/src/CommandLine/Console.php
+++ b/src/CommandLine/Console.php
@@ -20,24 +20,24 @@ class Console
 	public function __construct()
 	{
 		$this->useColors = PHP_SAPI === 'cli' && ((function_exists('posix_isatty') && posix_isatty(STDOUT))
-			|| getenv('ConEmuANSI') === 'ON' || getenv('ANSICON') !== FALSE || getenv('term') === 'xterm-256color');
+			|| getenv('ConEmuANSI') === 'ON' || getenv('ANSICON') !== false || getenv('term') === 'xterm-256color');
 	}
 
 
-	public function useColors($state = TRUE)
+	public function useColors($state = true)
 	{
 		$this->useColors = (bool) $state;
 	}
 
 
-	public function color($color = NULL, $s = NULL)
+	public function color($color = null, $s = null)
 	{
 		static $colors = [
 			'black' => '0;30', 'gray' => '1;30', 'silver' => '0;37', 'white' => '1;37',
 			'navy' => '0;34', 'blue' => '1;34', 'green' => '0;32', 'lime' => '1;32',
 			'teal' => '0;36', 'aqua' => '1;36', 'maroon' => '0;31', 'red' => '1;31',
 			'purple' => '0;35', 'fuchsia' => '1;35', 'olive' => '0;33', 'yellow' => '1;33',
-			NULL => '0',
+			null => '0',
 		];
 		if ($this->useColors) {
 			$c = explode('/', $color);
@@ -45,7 +45,7 @@ public function color($color = NULL, $s = NULL)
 				. ($c[0] ? $colors[$c[0]] : '')
 				. (empty($c[1]) ? '' : ';4' . substr($colors[$c[1]], -1))
 				. 'm' . $s
-				. ($s === NULL ? '' : "\033[0m");
+				. ($s === null ? '' : "\033[0m");
 		}
 		return $s;
 	}
diff --git a/src/CommandLine/Parser.php b/src/CommandLine/Parser.php
index c830ba2..64df047 100644
--- a/src/CommandLine/Parser.php
+++ b/src/CommandLine/Parser.php
@@ -52,8 +52,8 @@ public function __construct($help, array $defaults = [])
 				self::ARGUMENT => (bool) end($m[2]),
 				self::OPTIONAL => isset($line[2]) || (substr(end($m[2]), 0, 1) === '[') || isset($opts[self::VALUE]),
 				self::REPEATABLE => (bool) end($m[3]),
-				self::ENUM => count($enums = explode('|', trim(end($m[2]), '<[]>'))) > 1 ? $enums : NULL,
-				self::VALUE => isset($line[2]) ? $line[2] : NULL,
+				self::ENUM => count($enums = explode('|', trim(end($m[2]), '<[]>'))) > 1 ? $enums : null,
+				self::VALUE => isset($line[2]) ? $line[2] : null,
 			];
 			if ($name !== $m[1][0]) {
 				$this->aliases[$m[1][0]] = $name;
@@ -68,9 +68,9 @@ public function __construct($help, array $defaults = [])
 	}
 
 
-	public function parse(array $args = NULL)
+	public function parse(array $args = null)
 	{
-		if ($args === NULL) {
+		if ($args === null) {
 			$args = isset($_SERVER['argv']) ? array_slice($_SERVER['argv'], 1) : [];
 		}
 		$params = [];
@@ -93,7 +93,7 @@ public function parse(array $args = NULL)
 				continue;
 			}
 
-			list($name, $arg) = strpos($arg, '=') ? explode('=', $arg, 2) : [$arg, TRUE];
+			list($name, $arg) = strpos($arg, '=') ? explode('=', $arg, 2) : [$arg, true];
 
 			if (isset($this->aliases[$name])) {
 				$name = $this->aliases[$name];
@@ -104,10 +104,10 @@ public function parse(array $args = NULL)
 
 			$opt = $this->options[$name];
 
-			if ($arg !== TRUE && empty($opt[self::ARGUMENT])) {
+			if ($arg !== true && empty($opt[self::ARGUMENT])) {
 				throw new \Exception("Option $name has not argument.");
 
-			} elseif ($arg === TRUE && !empty($opt[self::ARGUMENT])) {
+			} elseif ($arg === true && !empty($opt[self::ARGUMENT])) {
 				if (isset($args[$i]) && $args[$i][0] !== '-') {
 					$arg = $args[$i++];
 				} elseif (empty($opt[self::OPTIONAL])) {
@@ -115,7 +115,7 @@ public function parse(array $args = NULL)
 				}
 			}
 
-			if (!empty($opt[self::ENUM]) && !in_array($arg, $opt[self::ENUM], TRUE) && !($opt[self::OPTIONAL] && $arg === TRUE)) {
+			if (!empty($opt[self::ENUM]) && !in_array($arg, $opt[self::ENUM], true) && !($opt[self::OPTIONAL] && $arg === true)) {
 				throw new \Exception("Value of option $name must be " . implode(', or ', $opt[self::ENUM]) . '.');
 			}
 			$this->checkArg($opt, $arg);
@@ -135,7 +135,7 @@ public function parse(array $args = NULL)
 			} elseif ($name[0] !== '-' && empty($opt[self::OPTIONAL])) {
 				throw new \Exception("Missing required argument <$name>.");
 			} else {
-				$params[$name] = NULL;
+				$params[$name] = null;
 			}
 			if (!empty($opt[self::REPEATABLE])) {
 				$params[$name] = (array) $params[$name];
@@ -155,7 +155,7 @@ public function checkArg(array $opt, &$arg)
 	{
 		if (!empty($opt[self::REALPATH])) {
 			$path = realpath($arg);
-			if ($path === FALSE) {
+			if ($path === false) {
 				throw new \Exception("File path '$arg' not found.");
 			}
 			$arg = $path;
diff --git a/tests/Console.color.phpt b/tests/Console.color.phpt
index 00eace1..d692dea 100644
--- a/tests/Console.color.phpt
+++ b/tests/Console.color.phpt
@@ -8,12 +8,12 @@ require __DIR__ . '/bootstrap.php';
 $console = new Console;
 $console->useColors();
 
-Assert::same("\x1b[m", $console->color(NULL));
+Assert::same("\x1b[m", $console->color(null));
 Assert::same("\x1b[1;31m", $console->color('red'));
 Assert::same("\x1b[1;31;42m", $console->color('red/green'));
 Assert::same("\x1b[1;31;42m", $console->color('red/lime'));
 
-Assert::same("\x1b[mhello\x1b[0m", $console->color(NULL, 'hello'));
+Assert::same("\x1b[mhello\x1b[0m", $console->color(null, 'hello'));
 Assert::same("\x1b[1;31mhello\x1b[0m", $console->color('red', 'hello'));
 Assert::same("\x1b[1;31;42mhello\x1b[0m", $console->color('red/green', 'hello'));
 Assert::same("\x1b[1;31;42mhello\x1b[0m", $console->color('red/lime', 'hello'));
diff --git a/tests/Parser.phpt b/tests/Parser.phpt
index 87b3c22..fdb0c4b 100644
--- a/tests/Parser.phpt
+++ b/tests/Parser.phpt
@@ -14,15 +14,15 @@ test(function () {
 		--a-b
 	');
 
-	Assert::same(['-p' => NULL, '--p' => NULL, '--a-b' => NULL], $cmd->parse([]));
-	Assert::same(['-p' => TRUE, '--p' => NULL, '--a-b' => NULL], $cmd->parse(['-p']));
+	Assert::same(['-p' => null, '--p' => null, '--a-b' => null], $cmd->parse([]));
+	Assert::same(['-p' => true, '--p' => null, '--a-b' => null], $cmd->parse(['-p']));
 
 	$cmd = new Parser('
 		-p  description
 	');
 
-	Assert::same(['-p' => NULL], $cmd->parse([]));
-	Assert::same(['-p' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['-p' => null], $cmd->parse([]));
+	Assert::same(['-p' => true], $cmd->parse(['-p']));
 });
 
 
@@ -32,7 +32,7 @@ test(function () { // default value
 	');
 
 	Assert::same(['-p' => '123'], $cmd->parse([]));
-	Assert::same(['-p' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['-p' => true], $cmd->parse(['-p']));
 
 
 	$cmd = new Parser('
@@ -42,7 +42,7 @@ test(function () { // default value
 	]);
 
 	Assert::same(['-p' => 123], $cmd->parse([]));
-	Assert::same(['-p' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['-p' => true], $cmd->parse(['-p']));
 });
 
 
@@ -51,10 +51,10 @@ test(function () { // alias
 		-p | --param
 	');
 
-	Assert::same(['--param' => NULL], $cmd->parse([]));
-	Assert::same(['--param' => TRUE], $cmd->parse(['-p']));
-	Assert::same(['--param' => TRUE], $cmd->parse(['--param']));
-	Assert::same(['--param' => TRUE], $cmd->parse(explode(' ', '-p --param')));
+	Assert::same(['--param' => null], $cmd->parse([]));
+	Assert::same(['--param' => true], $cmd->parse(['-p']));
+	Assert::same(['--param' => true], $cmd->parse(['--param']));
+	Assert::same(['--param' => true], $cmd->parse(explode(' ', '-p --param')));
 	Assert::exception(function () use ($cmd) {
 		$cmd->parse(['-p=val']);
 	}, 'Exception', 'Option --param has not argument.');
@@ -63,13 +63,13 @@ test(function () { // alias
 		-p --param
 	');
 
-	Assert::same(['--param' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['--param' => true], $cmd->parse(['-p']));
 
 	$cmd = new Parser('
 		-p, --param
 	');
 
-	Assert::same(['--param' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['--param' => true], $cmd->parse(['-p']));
 });
 
 
@@ -78,7 +78,7 @@ test(function () { // argument
 		-p param
 	');
 
-	Assert::same(['-p' => NULL], $cmd->parse([]));
+	Assert::same(['-p' => null], $cmd->parse([]));
 	Assert::same(['-p' => 'val'], $cmd->parse(explode(' ', '-p val')));
 	Assert::same(['-p' => 'val'], $cmd->parse(explode(' ', '-p=val')));
 	Assert::same(['-p' => 'val2'], $cmd->parse(explode(' ', '-p val1 -p val2')));
@@ -106,8 +106,8 @@ test(function () { // optional argument
 		-p [param]
 	');
 
-	Assert::same(['-p' => NULL], $cmd->parse([]));
-	Assert::same(['-p' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['-p' => null], $cmd->parse([]));
+	Assert::same(['-p' => true], $cmd->parse(['-p']));
 	Assert::same(['-p' => 'val'], $cmd->parse(explode(' ', '-p val')));
 
 
@@ -118,18 +118,18 @@ test(function () { // optional argument
 	]);
 
 	Assert::same(['-p' => 123], $cmd->parse([]));
-	Assert::same(['-p' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['-p' => true], $cmd->parse(['-p']));
 	Assert::same(['-p' => 'val'], $cmd->parse(explode(' ', '-p val')));
 
 
 	$cmd = new Parser('
 		-p param
 	', [
-		'-p' => [Parser::OPTIONAL => TRUE],
+		'-p' => [Parser::OPTIONAL => true],
 	]);
 
-	Assert::same(['-p' => NULL], $cmd->parse([]));
-	Assert::same(['-p' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['-p' => null], $cmd->parse([]));
+	Assert::same(['-p' => true], $cmd->parse(['-p']));
 	Assert::same(['-p' => 'val'], $cmd->parse(explode(' ', '-p val')));
 });
 
@@ -141,7 +141,7 @@ test(function () { // repeatable argument
 	');
 
 	Assert::same(['-p' => []], $cmd->parse([]));
-	Assert::same(['-p' => [TRUE]], $cmd->parse(['-p']));
+	Assert::same(['-p' => [true]], $cmd->parse(['-p']));
 	Assert::same(['-p' => ['val']], $cmd->parse(explode(' ', '-p val')));
 	Assert::same(['-p' => ['val1', 'val2']], $cmd->parse(explode(' ', '-p val1 -p val2')));
 });
@@ -153,7 +153,7 @@ test(function () { // enumerates
 		-p <a|b|c>
 	');
 
-	Assert::same(['-p' => NULL], $cmd->parse([]));
+	Assert::same(['-p' => null], $cmd->parse([]));
 	Assert::exception(function () use ($cmd) {
 		$cmd->parse(['-p']);
 	}, 'Exception', 'Option -p requires argument.');
@@ -167,8 +167,8 @@ test(function () { // enumerates
 		-p [a|b|c]
 	');
 
-	Assert::same(['-p' => NULL], $cmd->parse([]));
-	Assert::same(['-p' => TRUE], $cmd->parse(['-p']));
+	Assert::same(['-p' => null], $cmd->parse([]));
+	Assert::same(['-p' => true], $cmd->parse(['-p']));
 	Assert::same(['-p' => 'a'], $cmd->parse(explode(' ', '-p a')));
 	Assert::exception(function () use ($cmd) {
 		$cmd->parse(explode(' ', '-p foo'));
@@ -181,7 +181,7 @@ test(function () { // realpath
 	$cmd = new Parser('
 		-p <path>
 	', [
-		'-p' => [Parser::REALPATH => TRUE],
+		'-p' => [Parser::REALPATH => true],
 	]);
 
 	Assert::exception(function () use ($cmd) {
@@ -208,21 +208,21 @@ test(function () { // positional arguments
 	}, 'Exception', 'Unexpected parameter val2.');
 
 	$cmd = new Parser('', [
-		'pos' => [Parser::REPEATABLE => TRUE],
+		'pos' => [Parser::REPEATABLE => true],
 	]);
 
 	Assert::same(['pos' => ['val1', 'val2']], $cmd->parse(['val1', 'val2']));
 
 
 	$cmd = new Parser('', [
-		'pos' => [Parser::OPTIONAL => TRUE],
+		'pos' => [Parser::OPTIONAL => true],
 	]);
 
-	Assert::same(['pos' => NULL], $cmd->parse([]));
+	Assert::same(['pos' => null], $cmd->parse([]));
 
 
 	$cmd = new Parser('', [
-		'pos' => [Parser::VALUE => 'default', Parser::REPEATABLE => TRUE],
+		'pos' => [Parser::VALUE => 'default', Parser::REPEATABLE => true],
 	]);
 
 	Assert::same(['pos' => ['default']], $cmd->parse([]));