diff --git a/src/AstRuntime.php b/src/AstRuntime.php
index db8a60e..03f5f1a 100644
--- a/src/AstRuntime.php
+++ b/src/AstRuntime.php
@@ -29,7 +29,7 @@ public function __construct(
      *                           is similar to data returned from json_decode
      *                           using associative arrays rather than objects.
      *
-     * @return mixed|null Returns the matching data or null
+     * @return mixed Returns the matching data or null
      */
     public function __invoke($expression, $data)
     {
diff --git a/src/CompilerRuntime.php b/src/CompilerRuntime.php
index f2becb9..c26b09c 100644
--- a/src/CompilerRuntime.php
+++ b/src/CompilerRuntime.php
@@ -19,8 +19,8 @@ class CompilerRuntime
     private $interpreter;
 
     /**
-     * @param string $dir Directory used to store compiled PHP files.
-     * @param Parser $parser JMESPath parser to utilize
+     * @param string|null $dir Directory used to store compiled PHP files.
+     * @param Parser|null $parser JMESPath parser to utilize
      * @throws \RuntimeException if the cache directory cannot be created
      */
     public function __construct($dir = null, Parser $parser = null)
@@ -46,7 +46,7 @@ public function __construct($dir = null, Parser $parser = null)
      *                           is similar to data returned from json_decode
      *                           using associative arrays rather than objects.
      *
-     * @return mixed|null Returns the matching data or null
+     * @return mixed Returns the matching data or null
      * @throws \RuntimeException
      */
     public function __invoke($expression, $data)
diff --git a/src/Env.php b/src/Env.php
index 9472d72..b22cf25 100644
--- a/src/Env.php
+++ b/src/Env.php
@@ -20,7 +20,7 @@ final class Env
      * @param string $expression JMESPath expression to evaluate
      * @param mixed  $data       JSON-like data to search
      *
-     * @return mixed|null Returns the matching data or null
+     * @return mixed Returns the matching data or null
      */
     public static function search($expression, $data)
     {
diff --git a/src/JmesPath.php b/src/JmesPath.php
index e2c239a..d24e516 100644
--- a/src/JmesPath.php
+++ b/src/JmesPath.php
@@ -7,7 +7,7 @@
  * @param string $expression Expression to search.
  * @param mixed $data Data to search.
  *
- * @return mixed|null
+ * @return mixed
  */
 if (!function_exists(__NAMESPACE__ . '\search')) {
     function search($expression, $data)
diff --git a/src/Parser.php b/src/Parser.php
index 1b875da..0733f20 100644
--- a/src/Parser.php
+++ b/src/Parser.php
@@ -55,7 +55,7 @@ class Parser
     ];
 
     /**
-     * @param Lexer $lexer Lexer used to tokenize expressions
+     * @param Lexer|null $lexer Lexer used to tokenize expressions
      */
     public function __construct(Lexer $lexer = null)
     {
diff --git a/src/TreeInterpreter.php b/src/TreeInterpreter.php
index cdfdd99..934c506 100644
--- a/src/TreeInterpreter.php
+++ b/src/TreeInterpreter.php
@@ -10,9 +10,9 @@ class TreeInterpreter
     private $fnDispatcher;
 
     /**
-     * @param callable $fnDispatcher Function dispatching function that accepts
-     *                               a function name argument and an array of
-     *                               function arguments and returns the result.
+     * @param callable|null $fnDispatcher Function dispatching function that accepts
+     *                                    a function name argument and an array of
+     *                                    function arguments and returns the result.
      */
     public function __construct(callable $fnDispatcher = null)
     {