diff --git a/src/PhpSpreadsheet/Shared/StringHelper.php b/src/PhpSpreadsheet/Shared/StringHelper.php
index 9a8fa86551..66800f179c 100644
--- a/src/PhpSpreadsheet/Shared/StringHelper.php
+++ b/src/PhpSpreadsheet/Shared/StringHelper.php
@@ -35,7 +35,7 @@ class StringHelper
     /**
      * Currency code.
      *
-     * @var string
+     * @var ?string
      */
     private static $currencyCode;
 
@@ -551,9 +551,9 @@ public static function getDecimalSeparator(): string
      * Set the decimal separator. Only used by NumberFormat::toFormattedString()
      * to format output by \PhpOffice\PhpSpreadsheet\Writer\Html and \PhpOffice\PhpSpreadsheet\Writer\Pdf.
      *
-     * @param string $separator Character for decimal separator
+     * @param ?string $separator Character for decimal separator
      */
-    public static function setDecimalSeparator(string $separator): void
+    public static function setDecimalSeparator(?string $separator): void
     {
         self::$decimalSeparator = $separator;
     }
@@ -582,9 +582,9 @@ public static function getThousandsSeparator(): string
      * Set the thousands separator. Only used by NumberFormat::toFormattedString()
      * to format output by \PhpOffice\PhpSpreadsheet\Writer\Html and \PhpOffice\PhpSpreadsheet\Writer\Pdf.
      *
-     * @param string $separator Character for thousands separator
+     * @param ?string $separator Character for thousands separator
      */
-    public static function setThousandsSeparator(string $separator): void
+    public static function setThousandsSeparator(?string $separator): void
     {
         self::$thousandsSeparator = $separator;
     }
@@ -618,9 +618,9 @@ public static function getCurrencyCode(): string
      * Set the currency code. Only used by NumberFormat::toFormattedString()
      *        to format output by \PhpOffice\PhpSpreadsheet\Writer\Html and \PhpOffice\PhpSpreadsheet\Writer\Pdf.
      *
-     * @param string $currencyCode Character for currency code
+     * @param ?string $currencyCode Character for currency code
      */
-    public static function setCurrencyCode(string $currencyCode): void
+    public static function setCurrencyCode(?string $currencyCode): void
     {
         self::$currencyCode = $currencyCode;
     }
diff --git a/src/PhpSpreadsheet/Style/NumberFormat/BaseFormatter.php b/src/PhpSpreadsheet/Style/NumberFormat/BaseFormatter.php
index 7988143c51..d6f373d079 100644
--- a/src/PhpSpreadsheet/Style/NumberFormat/BaseFormatter.php
+++ b/src/PhpSpreadsheet/Style/NumberFormat/BaseFormatter.php
@@ -2,6 +2,8 @@
 
 namespace PhpOffice\PhpSpreadsheet\Style\NumberFormat;
 
+use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
+
 abstract class BaseFormatter
 {
     protected static function stripQuotes(string $format): string
@@ -9,4 +11,15 @@ protected static function stripQuotes(string $format): string
         // Some non-number strings are quoted, so we'll get rid of the quotes, likewise any positional * symbols
         return str_replace(['"', '*'], '', $format);
     }
+
+    protected static function adjustSeparators(string $value): string
+    {
+        $thousandsSeparator = StringHelper::getThousandsSeparator();
+        $decimalSeparator = StringHelper::getDecimalSeparator();
+        if ($thousandsSeparator !== ',' || $decimalSeparator !== '.') {
+            $value = str_replace(['.', ',', "\u{fffd}"], ["\u{fffd}", '.', ','], $value);
+        }
+
+        return $value;
+    }
 }
diff --git a/src/PhpSpreadsheet/Style/NumberFormat/Formatter.php b/src/PhpSpreadsheet/Style/NumberFormat/Formatter.php
index 1115467de4..f7969a449a 100644
--- a/src/PhpSpreadsheet/Style/NumberFormat/Formatter.php
+++ b/src/PhpSpreadsheet/Style/NumberFormat/Formatter.php
@@ -8,7 +8,7 @@
 use PhpOffice\PhpSpreadsheet\Style\Color;
 use PhpOffice\PhpSpreadsheet\Style\NumberFormat;
 
-class Formatter
+class Formatter extends BaseFormatter
 {
     /**
      * Matches any @ symbol that isn't enclosed in quotes.
@@ -133,7 +133,7 @@ public static function toFormattedString($value, $format, $callBack = null)
         // For 'General' format code, we just pass the value although this is not entirely the way Excel does it,
         // it seems to round numbers to a total of 10 digits.
         if (($format === NumberFormat::FORMAT_GENERAL) || ($format === NumberFormat::FORMAT_TEXT)) {
-            return (string) $value;
+            return self::adjustSeparators((string) $value);
         }
 
         // Ignore square-$-brackets prefix in format string, like "[$-411]ge.m.d", "[$-010419]0%", etc
diff --git a/src/PhpSpreadsheet/Style/NumberFormat/NumberFormatter.php b/src/PhpSpreadsheet/Style/NumberFormat/NumberFormatter.php
index f927964d37..6a6934524c 100644
--- a/src/PhpSpreadsheet/Style/NumberFormat/NumberFormatter.php
+++ b/src/PhpSpreadsheet/Style/NumberFormat/NumberFormatter.php
@@ -5,7 +5,7 @@
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
 use PhpOffice\PhpSpreadsheet\Style\NumberFormat;
 
-class NumberFormatter
+class NumberFormatter extends BaseFormatter
 {
     private const NUMBER_REGEX = '/(0+)(\\.?)(0*)/';
 
@@ -176,11 +176,11 @@ private static function formatStraightNumericValue(mixed $value, string $format,
             return $result;
         }
 
-        $sprintf_pattern = "%0$minWidth." . strlen($right) . 'f';
+        $sprintf_pattern = "%0$minWidth." . strlen($right) . 'F';
 
         /** @var float */
         $valueFloat = $value;
-        $value = sprintf($sprintf_pattern, round($valueFloat, strlen($right)));
+        $value = self::adjustSeparators(sprintf($sprintf_pattern, round($valueFloat, strlen($right))));
 
         return self::pregReplace(self::NUMBER_REGEX, $value, $format);
     }
diff --git a/src/PhpSpreadsheet/Style/NumberFormat/PercentageFormatter.php b/src/PhpSpreadsheet/Style/NumberFormat/PercentageFormatter.php
index 55b5971aa9..6d23f9ddfa 100644
--- a/src/PhpSpreadsheet/Style/NumberFormat/PercentageFormatter.php
+++ b/src/PhpSpreadsheet/Style/NumberFormat/PercentageFormatter.php
@@ -38,11 +38,11 @@ public static function format($value, string $format): string
 
         $wholePartSize += $decimalPartSize + (int) ($decimalPartSize > 0);
         $replacement = "0{$wholePartSize}.{$decimalPartSize}";
-        $mask = (string) preg_replace('/[#0,]+\.?[?#0,]*/ui', "%{$replacement}f{$placeHolders}", $format);
+        $mask = (string) preg_replace('/[#0,]+\.?[?#0,]*/ui', "%{$replacement}F{$placeHolders}", $format);
 
         /** @var float */
         $valueFloat = $value;
 
-        return sprintf($mask, round($valueFloat, $decimalPartSize));
+        return self::adjustSeparators(sprintf($mask, round($valueFloat, $decimalPartSize)));
     }
 }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberSlashTest.php b/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberSlashTest.php
index 9196bcc32a..c23f738709 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberSlashTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Engine/FormattedNumberSlashTest.php
@@ -10,24 +10,11 @@
 
 class FormattedNumberSlashTest extends TestCase
 {
-    private string $originalCurrencyCode;
-
-    private string $originalDecimalSeparator;
-
-    private string $originalThousandsSeparator;
-
-    protected function setUp(): void
-    {
-        $this->originalCurrencyCode = StringHelper::getCurrencyCode();
-        $this->originalDecimalSeparator = StringHelper::getDecimalSeparator();
-        $this->originalThousandsSeparator = StringHelper::getThousandsSeparator();
-    }
-
     protected function tearDown(): void
     {
-        StringHelper::setCurrencyCode($this->originalCurrencyCode);
-        StringHelper::setDecimalSeparator($this->originalDecimalSeparator);
-        StringHelper::setThousandsSeparator($this->originalThousandsSeparator);
+        StringHelper::setCurrencyCode(null);
+        StringHelper::setDecimalSeparator(null);
+        StringHelper::setThousandsSeparator(null);
     }
 
     /**
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueTest.php
index c04dfe8798..2df5db47bd 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ValueTest.php
@@ -9,26 +9,12 @@
 
 class ValueTest extends AllSetupTeardown
 {
-    private string $currencyCode;
-
-    private string $decimalSeparator;
-
-    private string $thousandsSeparator;
-
-    protected function setUp(): void
-    {
-        parent::setUp();
-        $this->currencyCode = StringHelper::getCurrencyCode();
-        $this->decimalSeparator = StringHelper::getDecimalSeparator();
-        $this->thousandsSeparator = StringHelper::getThousandsSeparator();
-    }
-
     protected function tearDown(): void
     {
         parent::tearDown();
-        StringHelper::setCurrencyCode($this->currencyCode);
-        StringHelper::setDecimalSeparator($this->decimalSeparator);
-        StringHelper::setThousandsSeparator($this->thousandsSeparator);
+        StringHelper::setCurrencyCode(null);
+        StringHelper::setDecimalSeparator(null);
+        StringHelper::setThousandsSeparator(null);
     }
 
     /**
diff --git a/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php b/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
index 9963f01f6c..3ab89878bf 100644
--- a/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php
@@ -18,20 +18,11 @@ class AdvancedValueBinderTest extends TestCase
 
     private string $originalLocale;
 
-    private string $originalCurrencyCode;
-
-    private string $originalDecimalSeparator;
-
-    private string $originalThousandsSeparator;
-
     private IValueBinder $valueBinder;
 
     protected function setUp(): void
     {
         $this->originalLocale = Settings::getLocale();
-        $this->originalCurrencyCode = StringHelper::getCurrencyCode();
-        $this->originalDecimalSeparator = StringHelper::getDecimalSeparator();
-        $this->originalThousandsSeparator = StringHelper::getThousandsSeparator();
 
         $this->valueBinder = Cell::getValueBinder();
         Cell::setValueBinder(new AdvancedValueBinder());
@@ -39,9 +30,9 @@ protected function setUp(): void
 
     protected function tearDown(): void
     {
-        StringHelper::setCurrencyCode($this->originalCurrencyCode);
-        StringHelper::setDecimalSeparator($this->originalDecimalSeparator);
-        StringHelper::setThousandsSeparator($this->originalThousandsSeparator);
+        StringHelper::setCurrencyCode(null);
+        StringHelper::setDecimalSeparator(null);
+        StringHelper::setThousandsSeparator(null);
         Settings::setLocale($this->originalLocale);
         Cell::setValueBinder($this->valueBinder);
     }
diff --git a/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatLocaleTest.php b/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatLocaleTest.php
index 9550636b3c..d6d65329e9 100644
--- a/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatLocaleTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Csv/CsvNumberFormatLocaleTest.php
@@ -31,7 +31,7 @@ protected function setUp(): void
     {
         $this->currentLocale = setlocale(LC_ALL, '0');
 
-        if (!setlocale(LC_ALL, 'de_DE.UTF-8', 'deu_deu')) {
+        if (!setlocale(LC_ALL, 'de_DE.UTF-8', 'deu_deu.utf8')) {
             $this->localeAdjusted = false;
 
             return;
@@ -52,6 +52,8 @@ protected function tearDown(): void
 
     /**
      * @dataProvider providerNumberFormatNoConversionTest
+     *
+     * @runInSeparateProcess
      */
     public function testNumberFormatNoConversion(mixed $expectedValue, string $expectedFormat, string $cellAddress): void
     {
diff --git a/tests/PhpSpreadsheetTests/Shared/StringHelperTest.php b/tests/PhpSpreadsheetTests/Shared/StringHelperTest.php
index e77e02a424..03a4403d1a 100644
--- a/tests/PhpSpreadsheetTests/Shared/StringHelperTest.php
+++ b/tests/PhpSpreadsheetTests/Shared/StringHelperTest.php
@@ -9,25 +9,11 @@
 
 class StringHelperTest extends TestCase
 {
-    private string $currencyCode;
-
-    private string $decimalSeparator;
-
-    private string $thousandsSeparator;
-
-    protected function setUp(): void
-    {
-        parent::setUp();
-        $this->currencyCode = StringHelper::getCurrencyCode();
-        $this->decimalSeparator = StringHelper::getDecimalSeparator();
-        $this->thousandsSeparator = StringHelper::getThousandsSeparator();
-    }
-
     protected function tearDown(): void
     {
-        StringHelper::setCurrencyCode($this->currencyCode);
-        StringHelper::setDecimalSeparator($this->decimalSeparator);
-        StringHelper::setThousandsSeparator($this->thousandsSeparator);
+        StringHelper::setCurrencyCode(null);
+        StringHelper::setDecimalSeparator(null);
+        StringHelper::setThousandsSeparator(null);
     }
 
     public function testGetIsIconvEnabled(): void
diff --git a/tests/PhpSpreadsheetTests/Style/NumberFormatTest.php b/tests/PhpSpreadsheetTests/Style/NumberFormatTest.php
index 5cd09574c8..0a1aaf2920 100644
--- a/tests/PhpSpreadsheetTests/Style/NumberFormatTest.php
+++ b/tests/PhpSpreadsheetTests/Style/NumberFormatTest.php
@@ -11,26 +11,17 @@
 
 class NumberFormatTest extends TestCase
 {
-    private string $currencyCode;
-
-    private string $decimalSeparator;
-
-    private string $thousandsSeparator;
-
     protected function setUp(): void
     {
-        $this->currencyCode = StringHelper::getCurrencyCode();
-        $this->decimalSeparator = StringHelper::getDecimalSeparator();
-        $this->thousandsSeparator = StringHelper::getThousandsSeparator();
         StringHelper::setDecimalSeparator('.');
         StringHelper::setThousandsSeparator(',');
     }
 
     protected function tearDown(): void
     {
-        StringHelper::setCurrencyCode($this->currencyCode);
-        StringHelper::setDecimalSeparator($this->decimalSeparator);
-        StringHelper::setThousandsSeparator($this->thousandsSeparator);
+        StringHelper::setCurrencyCode(null);
+        StringHelper::setDecimalSeparator(null);
+        StringHelper::setThousandsSeparator(null);
     }
 
     /**
diff --git a/tests/PhpSpreadsheetTests/Writer/Html/HtmlNumberFormatTest.php b/tests/PhpSpreadsheetTests/Writer/Html/HtmlNumberFormatTest.php
index 1594a6fa34..f792f92523 100644
--- a/tests/PhpSpreadsheetTests/Writer/Html/HtmlNumberFormatTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Html/HtmlNumberFormatTest.php
@@ -13,27 +13,18 @@
 
 class HtmlNumberFormatTest extends Functional\AbstractFunctional
 {
-    private string $currency;
-
-    private string $decsep;
-
-    private string $thosep;
-
     protected function setUp(): void
     {
-        $this->currency = StringHelper::getCurrencyCode();
         StringHelper::setCurrencyCode('$');
-        $this->decsep = StringHelper::getDecimalSeparator();
         StringHelper::setDecimalSeparator('.');
-        $this->thosep = StringHelper::getThousandsSeparator();
         StringHelper::setThousandsSeparator(',');
     }
 
     protected function tearDown(): void
     {
-        StringHelper::setCurrencyCode($this->currency);
-        StringHelper::setDecimalSeparator($this->decsep);
-        StringHelper::setThousandsSeparator($this->thosep);
+        StringHelper::setCurrencyCode(null);
+        StringHelper::setDecimalSeparator(null);
+        StringHelper::setThousandsSeparator(null);
     }
 
     public function testColorNumberFormat(): void
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/LocaleFloatsTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/LocaleFloatsTest.php
index 185154e1bd..5902896e7c 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xlsx/LocaleFloatsTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/LocaleFloatsTest.php
@@ -4,17 +4,18 @@
 
 namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
 
+use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
+use PhpOffice\PhpSpreadsheet\Settings;
+use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Style\NumberFormat;
 use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
 
 class LocaleFloatsTest extends AbstractFunctional
 {
-    private bool $localeAdjusted;
+    private false|string $currentPhpLocale;
 
-    /**
-     * @var false|string
-     */
-    private $currentLocale;
+    private string $originalLocale;
 
     /** @var ?Spreadsheet */
     private $spreadsheet;
@@ -24,21 +25,19 @@ class LocaleFloatsTest extends AbstractFunctional
 
     protected function setUp(): void
     {
-        $this->currentLocale = setlocale(LC_ALL, '0');
-
-        if (!setlocale(LC_ALL, 'fr_FR.UTF-8', 'fra_fra')) {
-            $this->localeAdjusted = false;
-
-            return;
-        }
-
-        $this->localeAdjusted = true;
+        $this->currentPhpLocale = setlocale(LC_ALL, '0');
+        $this->originalLocale = Settings::getLocale();
+        StringHelper::setDecimalSeparator(null);
+        StringHelper::setThousandsSeparator(null);
     }
 
     protected function tearDown(): void
     {
-        if ($this->localeAdjusted && is_string($this->currentLocale)) {
-            setlocale(LC_ALL, $this->currentLocale);
+        StringHelper::setDecimalSeparator(null);
+        StringHelper::setThousandsSeparator(null);
+        Settings::setLocale($this->originalLocale);
+        if ($this->currentPhpLocale !== false) {
+            setlocale(LC_ALL, $this->currentPhpLocale);
         }
         if ($this->spreadsheet !== null) {
             $this->spreadsheet->disconnectWorksheets();
@@ -50,12 +49,17 @@ protected function tearDown(): void
         }
     }
 
+    /**
+     * Use separate process because this calls native Php setlocale.
+     *
+     * @runInSeparateProcess
+     */
     public function testLocaleFloatsCorrectlyConvertedByWriter(): void
     {
-        if (!$this->localeAdjusted) {
+        if (!setlocale(LC_ALL, 'fr_FR.UTF-8', 'fra_fra.utf8')) {
+            $this->currentPhpLocale = false;
             self::markTestSkipped('Unable to set locale for testing.');
         }
-
         $this->spreadsheet = $spreadsheet = new Spreadsheet();
         $properties = $spreadsheet->getProperties();
         $properties->setCustomProperty('Version', 1.2);
@@ -68,7 +72,67 @@ public function testLocaleFloatsCorrectlyConvertedByWriter(): void
         $prop = $reloadedSpreadsheet->getProperties()->getCustomPropertyValue('Version');
         self::assertEqualsWithDelta(1.2, $prop, 1.0E-8);
 
-        $actual = sprintf('%f', $result);
+        $actual = $reloadedSpreadsheet->getActiveSheet()->getCell('A1')->getFormattedValue();
         self::assertStringContainsString('1,1', $actual);
     }
+
+    public function testPercentageStoredAsString(): void
+    {
+        Settings::setLocale('fr_FR');
+        StringHelper::setDecimalSeparator(',');
+        StringHelper::setThousandsSeparator('.');
+        $reader = new XlsxReader();
+        $this->spreadsheet = $spreadsheet = $reader->load('tests/data/Writer/Xlsx/issue.3811b.xlsx');
+        $sheet = $spreadsheet->getActiveSheet();
+        self::assertSame('48,34%', $sheet->getCell('L2')->getValue());
+        self::assertIsString($sheet->getCell('L2')->getValue());
+        self::assertSame('=(10%+L2)/2', $sheet->getCell('L1')->getValue());
+        self::assertEqualsWithDelta(0.2917, $sheet->getCell('L1')->getCalculatedValue(), 1E-8);
+        self::assertIsFloat($sheet->getCell('L1')->getCalculatedValue());
+        self::assertEquals('29,17%', $sheet->getCell('L1')->getFormattedValue());
+
+        $sheet->getCell('A10')->setValue(3.2);
+        self::assertSame(NumberFormat::FORMAT_GENERAL, $sheet->getStyle('A10')->getNumberFormat()->getFormatCode());
+        self::assertSame('3,2', $sheet->getCell('A10')->getFormattedValue());
+        $sheet->getCell('A11')->setValue(1002.5);
+        $sheet->getStyle('A11')->getNumberFormat()->setFormatCode(NumberFormat::FORMAT_NUMBER_COMMA_SEPARATED1);
+        self::assertSame('1.002,50', $sheet->getCell('A11')->getFormattedValue());
+        $sheet->getCell('A12')->setValue(2.5);
+        $sheet->getStyle('A12')->getNumberFormat()->setFormatCode(NumberFormat::FORMAT_NUMBER_00);
+        self::assertSame('2,50', $sheet->getCell('A12')->getFormattedValue());
+    }
+
+    /**
+     * Use separate process because this calls native Php setlocale.
+     *
+     * @runInSeparateProcess
+     */
+    public function testPercentageStoredAsString2(): void
+    {
+        if (!setlocale(LC_ALL, 'fr_FR.UTF-8', 'fra_fra.utf8')) {
+            $this->currentPhpLocale = false;
+            self::markTestSkipped('Unable to set locale for testing.');
+        }
+        $reader = new XlsxReader();
+        $this->spreadsheet = $spreadsheet = $reader->load('tests/data/Writer/Xlsx/issue.3811b.xlsx');
+        $sheet = $spreadsheet->getActiveSheet();
+        self::assertSame('48,34%', $sheet->getCell('L2')->getValue());
+        self::assertIsString($sheet->getCell('L2')->getValue());
+        self::assertSame('=(10%+L2)/2', $sheet->getCell('L1')->getValue());
+        self::assertEqualsWithDelta(0.2917, $sheet->getCell('L1')->getCalculatedValue(), 1E-8);
+        self::assertIsFloat($sheet->getCell('L1')->getCalculatedValue());
+        self::assertEquals('29,17%', $sheet->getCell('L1')->getFormattedValue());
+
+        $sheet->getCell('A10')->setValue(3.2);
+        self::assertSame(NumberFormat::FORMAT_GENERAL, $sheet->getStyle('A10')->getNumberFormat()->getFormatCode());
+        self::assertSame('3,2', $sheet->getCell('A10')->getFormattedValue());
+        $narrowNonBreakSpace = "\u{202f}";
+        self::assertSame($narrowNonBreakSpace, localeconv()['thousands_sep']);
+        $sheet->getCell('A11')->setValue(1002.5);
+        $sheet->getStyle('A11')->getNumberFormat()->setFormatCode(NumberFormat::FORMAT_NUMBER_COMMA_SEPARATED1);
+        self::assertSame('1' . $narrowNonBreakSpace . '002,50', $sheet->getCell('A11')->getFormattedValue());
+        $sheet->getCell('A12')->setValue(2.5);
+        $sheet->getStyle('A12')->getNumberFormat()->setFormatCode(NumberFormat::FORMAT_NUMBER_00);
+        self::assertSame('2,50', $sheet->getCell('A12')->getFormattedValue());
+    }
 }
diff --git a/tests/data/Writer/XLSX/issue.3811b.xlsx b/tests/data/Writer/XLSX/issue.3811b.xlsx
new file mode 100644
index 0000000000..43dbf4bd8d
Binary files /dev/null and b/tests/data/Writer/XLSX/issue.3811b.xlsx differ