diff --git a/ChangeLog.md b/ChangeLog.md
index 9bdcc5b6..e62d8f95 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -2,6 +2,19 @@
 
 All notable changes are documented in this file using the [Keep a CHANGELOG](http://keepachangelog.com/) principles.
 
+## [4.0.6] - 2024-03-02
+
+### Changed
+
+* Do not use implicitly nullable parameters
+
+## [4.0.5] - 2023-05-07
+
+### Changed
+
+* [#118](https://github.com/sebastianbergmann/diff/pull/118): Improve performance of `MemoryEfficientLongestCommonSubsequenceCalculator`
+* [#119](https://github.com/sebastianbergmann/diff/pull/119): Improve performance of `TimeEfficientLongestCommonSubsequenceCalculator`
+
 ## [4.0.4] - 2020-10-26
 
 ### Fixed
@@ -76,6 +89,8 @@ All notable changes are documented in this file using the [Keep a CHANGELOG](htt
 
 * This component is no longer supported on PHP 5.6
 
+[4.0.6]: https://github.com/sebastianbergmann/diff/compare/4.0.5...4.0.6
+[4.0.5]: https://github.com/sebastianbergmann/diff/compare/4.0.4...4.0.5
 [4.0.4]: https://github.com/sebastianbergmann/diff/compare/4.0.3...4.0.4
 [4.0.3]: https://github.com/sebastianbergmann/diff/compare/4.0.2...4.0.3
 [4.0.2]: https://github.com/sebastianbergmann/diff/compare/4.0.1...4.0.2
diff --git a/src/Differ.php b/src/Differ.php
index 5a4d9d10..98c7a9b2 100644
--- a/src/Differ.php
+++ b/src/Differ.php
@@ -82,7 +82,7 @@ public function __construct($outputBuilder = null)
      * @param array|string $from
      * @param array|string $to
      */
-    public function diff($from, $to, LongestCommonSubsequenceCalculator $lcs = null): string
+    public function diff($from, $to, ?LongestCommonSubsequenceCalculator $lcs = null): string
     {
         $diff = $this->diffToArray(
             $this->normalizeDiffInput($from),
@@ -108,7 +108,7 @@ public function diff($from, $to, LongestCommonSubsequenceCalculator $lcs = null)
      * @param array|string                       $to
      * @param LongestCommonSubsequenceCalculator $lcs
      */
-    public function diffToArray($from, $to, LongestCommonSubsequenceCalculator $lcs = null): array
+    public function diffToArray($from, $to, ?LongestCommonSubsequenceCalculator $lcs = null): array
     {
         if (is_string($from)) {
             $from = $this->splitStringByLines($from);
diff --git a/src/Exception/ConfigurationException.php b/src/Exception/ConfigurationException.php
index b767b219..8847a2e5 100644
--- a/src/Exception/ConfigurationException.php
+++ b/src/Exception/ConfigurationException.php
@@ -22,7 +22,7 @@ public function __construct(
         string $expected,
         $value,
         int $code = 0,
-        Exception $previous = null
+        ?Exception $previous = null
     ) {
         parent::__construct(
             sprintf(
diff --git a/src/MemoryEfficientLongestCommonSubsequenceCalculator.php b/src/MemoryEfficientLongestCommonSubsequenceCalculator.php
index 0b626eaf..489113b6 100644
--- a/src/MemoryEfficientLongestCommonSubsequenceCalculator.php
+++ b/src/MemoryEfficientLongestCommonSubsequenceCalculator.php
@@ -78,7 +78,12 @@ private function length(array $from, array $to): array
                 if ($from[$i] === $to[$j]) {
                     $current[$j + 1] = $prev[$j] + 1;
                 } else {
-                    $current[$j + 1] = max($current[$j], $prev[$j + 1]);
+                    // don't use max() to avoid function call overhead
+                    if ($current[$j] > $prev[$j + 1]) {
+                        $current[$j + 1] = $current[$j];
+                    } else {
+                        $current[$j + 1] = $prev[$j + 1];
+                    }
                 }
             }
         }
diff --git a/src/TimeEfficientLongestCommonSubsequenceCalculator.php b/src/TimeEfficientLongestCommonSubsequenceCalculator.php
index fd19cac7..4e8d951d 100644
--- a/src/TimeEfficientLongestCommonSubsequenceCalculator.php
+++ b/src/TimeEfficientLongestCommonSubsequenceCalculator.php
@@ -37,12 +37,24 @@ public function calculate(array $from, array $to): array
 
         for ($i = 1; $i <= $fromLength; ++$i) {
             for ($j = 1; $j <= $toLength; ++$j) {
-                $o          = ($j * $width) + $i;
-                $matrix[$o] = max(
-                    $matrix[$o - 1],
-                    $matrix[$o - $width],
-                    $from[$i - 1] === $to[$j - 1] ? $matrix[$o - $width - 1] + 1 : 0
-                );
+                $o = ($j * $width) + $i;
+
+                // don't use max() to avoid function call overhead
+                $firstOrLast = $from[$i - 1] === $to[$j - 1] ? $matrix[$o - $width - 1] + 1 : 0;
+
+                if ($matrix[$o - 1] > $matrix[$o - $width]) {
+                    if ($firstOrLast > $matrix[$o - 1]) {
+                        $matrix[$o] = $firstOrLast;
+                    } else {
+                        $matrix[$o] = $matrix[$o - 1];
+                    }
+                } else {
+                    if ($firstOrLast > $matrix[$o - $width]) {
+                        $matrix[$o] = $firstOrLast;
+                    } else {
+                        $matrix[$o] = $matrix[$o - $width];
+                    }
+                }
             }
         }