diff --git a/CHANGELOG.md b/CHANGELOG.md
index 953dedaa64..e27b761a58 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,7 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 
 ### Fixed
 
-- Nothing yet.
+- Xls writer Parser Mishandling True/False Argument. [Issue #4331](https://github.com/PHPOffice/PhpSpreadsheet/issues/4331) [PR #4333](https://github.com/PHPOffice/PhpSpreadsheet/pull/4333)
 
 ## 2025-01-26 - 3.9.0
 
diff --git a/src/PhpSpreadsheet/Writer/Xls/Parser.php b/src/PhpSpreadsheet/Writer/Xls/Parser.php
index 52b4ad3538..ec1114a4a3 100644
--- a/src/PhpSpreadsheet/Writer/Xls/Parser.php
+++ b/src/PhpSpreadsheet/Writer/Xls/Parser.php
@@ -1624,7 +1624,9 @@ public function toReversePolish(array $tree = []): string
             }
 
             // add its left subtree and return.
-            return $left_tree . $this->convertFunction($tree['value'], $tree['right']);
+            if ($left_tree !== '' || $tree['right'] !== '') {
+                return $left_tree . $this->convertFunction($tree['value'], $tree['right'] ?: 0);
+            }
         }
         $converted_tree = $this->convert($tree['value']);
 
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/Issue4331Test.php b/tests/PhpSpreadsheetTests/Writer/Xls/Issue4331Test.php
new file mode 100644
index 0000000000..77841d8290
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/Issue4331Test.php
@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Xls;
+
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class Issue4331Test extends AbstractFunctional
+{
+    public function testIssue4331(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $c3 = '=VLOOKUP(B3,$B$10:$C$13,2,FALSE)';
+        $d3 = '=VLOOKUP("intermediate",$B$10:$C$13,2,TRUE)';
+        $c4 = '=VLOOKUP(B3,$B$10:$C$13,2,FALSE())';
+        $d4 = '=VLOOKUP("intermediate",$B$10:$C$13,2,TRUE())';
+        $sheet->fromArray(
+            [
+                ['level', 'result'],
+                ['medium', $c3, $d3],
+                [null, $c4, $d4],
+            ],
+            null,
+            'B2',
+            true
+        );
+        $sheet->fromArray(
+            [
+                ['high', 6],
+                ['low', 2],
+                ['medium', 4],
+                ['none', 0],
+            ],
+            null,
+            'B10',
+            true
+        );
+
+        $reloadedSpreadsheet = $this->writeAndReload($spreadsheet, 'Xls');
+        $spreadsheet->disconnectWorksheets();
+
+        $worksheet = $reloadedSpreadsheet->getActiveSheet();
+        self::assertSame($c3, $worksheet->getCell('C3')->getValue());
+        self::assertSame(4, $worksheet->getCell('C3')->getCalculatedValue());
+        self::assertSame($d3, $worksheet->getCell('D3')->getValue());
+        self::assertSame(6, $worksheet->getCell('D3')->getCalculatedValue());
+        self::assertSame($c4, $worksheet->getCell('C4')->getValue());
+        self::assertSame(4, $worksheet->getCell('C4')->getCalculatedValue());
+        self::assertSame($d4, $worksheet->getCell('D4')->getValue());
+        self::assertSame(6, $worksheet->getCell('D4')->getCalculatedValue());
+        $reloadedSpreadsheet->disconnectWorksheets();
+    }
+}