diff --git a/samples/Basic/16_Csv.php b/samples/Basic/16_Csv.php
index 15bbf0d4..137f6469 100644
--- a/samples/Basic/16_Csv.php
+++ b/samples/Basic/16_Csv.php
@@ -38,7 +38,8 @@ $helper->write($spreadsheetFromCSV, __FILE__, ['Xlsx']);
 $filenameCSV = $helper->getFilename(__FILE__, 'csv');
 /** @var \PhpOffice\PhpSpreadsheet\Writer\Csv $writerCSV */
 $writerCSV = new CsvWriter($spreadsheetFromCSV);
-$writerCSV->setExcelCompatibility(true);
+//$writerCSV->setExcelCompatibility(true);
+$writerCSV->setUseBom(true); // because of non-ASCII chars
 
 $callStartTime = microtime(true);
 $writerCSV->save($filenameCSV);
diff --git a/src/PhpSpreadsheet/Calculation/MathTrig/Sum.php b/src/PhpSpreadsheet/Calculation/MathTrig/Sum.php
index ab3a9a07..8a3223b1 100644
--- a/src/PhpSpreadsheet/Calculation/MathTrig/Sum.php
+++ b/src/PhpSpreadsheet/Calculation/MathTrig/Sum.php
@@ -51,16 +51,20 @@ class Sum
     {
         $returnValue = 0;
         // Loop through the arguments
-        foreach (Functions::flattenArray($args) as $arg) {
+        $aArgs = Functions::flattenArrayIndexed($args);
+        foreach ($aArgs as $k => $arg) {
             // Is it a numeric value?
             if (is_numeric($arg) || empty($arg)) {
                 if (is_string($arg)) {
                     $arg = (int) $arg;
                 }
                 $returnValue += $arg;
+            } elseif (is_bool($arg)) {
+                $returnValue += (int) $arg;
             } elseif (Functions::isError($arg)) {
                 return $arg;
-            } else {
+            // ignore non-numerics from cell, but fail as literals (except null)
+            } elseif ($arg !== null && !Functions::isCellValue($k)) {
                 return Functions::VALUE();
             }
         }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumTest.php
index a9ea7f29..b85f0c90 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/SumTest.php
@@ -26,4 +26,22 @@ class SumTest extends AllSetupTeardown
     {
         return require 'tests/data/Calculation/MathTrig/SUM.php';
     }
+
+    /**
+     * @dataProvider providerSUMLiterals
+     *
+     * @param mixed $expectedResult
+     */
+    public function testSUMLiterals($expectedResult, string $args): void
+    {
+        $sheet = $this->sheet;
+        $sheet->getCell('B1')->setValue("=SUM($args)");
+        $result = $sheet->getCell('B1')->getCalculatedValue();
+        self::assertEqualsWithDelta($expectedResult, $result, 1E-12);
+    }
+
+    public function providerSUMLiterals(): array
+    {
+        return require 'tests/data/Calculation/MathTrig/SUMLITERALS.php';
+    }
 }
diff --git a/tests/PhpSpreadsheetTests/Writer/Csv/CsvExcelCompatibilityTest.php b/tests/PhpSpreadsheetTests/Writer/Csv/CsvExcelCompatibilityTest.php
new file mode 100644
index 00000000..9b7d16aa
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Csv/CsvExcelCompatibilityTest.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Csv;
+
+use PhpOffice\PhpSpreadsheet\Reader\Csv as CsvReader;
+use PhpOffice\PhpSpreadsheet\Shared\File;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Writer\Csv as CsvWriter;
+use PhpOffice\PhpSpreadsheetTests\Functional;
+
+class CsvExcelCompatibilityTest extends Functional\AbstractFunctional
+{
+    // Excel seems to have changed with how they handle this.
+    // In particular, it does not recognize UTF-8 non-ASCII characters
+    //    if a file is written with ExcelCompatibility on.
+    //    The initial 'sep=;' line seems to confuse it, even though
+    //    it has a BOM. The Unix "file" command also indicates a difference
+    //    when the sep line is or is not included:
+    //        UTF-8 Unicode (with BOM) text, with CRLF line terminators
+    //     vs CSV text (without sep line, with or without BOM)
+    // So, this test has no UTF-8 yet while more research is conducted.
+    public function testExcelCompatibility(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->setCellValue('A1', '1');
+        $sheet->setCellValue('B1', '2');
+        $sheet->setCellValue('C1', '3');
+        $sheet->setCellValue('A2', '4');
+        $sheet->setCellValue('B2', '5');
+        $sheet->setCellValue('C2', '6');
+        $writer = new CsvWriter($spreadsheet);
+        $writer->setExcelCompatibility(true);
+        self::assertSame('', $writer->getOutputEncoding());
+        $filename = File::temporaryFilename();
+        $writer->save($filename);
+        $reader = new CsvReader();
+        $spreadsheet2 = $reader->load($filename);
+        $contents = file_get_contents($filename);
+        unlink($filename);
+        self::assertEquals(1, $spreadsheet2->getActiveSheet()->getCell('A1')->getValue());
+        self::assertEquals(6, $spreadsheet2->getActiveSheet()->getCell('C2')->getValue());
+        self::assertStringContainsString(CsvReader::UTF8_BOM, $contents);
+        self::assertStringContainsString("\r\n", $contents);
+        self::assertStringContainsString('sep=;', $contents);
+        self::assertStringContainsString('"1";"2";"3"', $contents);
+        self::assertStringContainsString('"4";"5";"6"', $contents);
+    }
+}
diff --git a/tests/data/Calculation/MathTrig/SUM.php b/tests/data/Calculation/MathTrig/SUM.php
index a8219076..0c54613e 100644
--- a/tests/data/Calculation/MathTrig/SUM.php
+++ b/tests/data/Calculation/MathTrig/SUM.php
@@ -4,5 +4,9 @@ return [
     [50, 5, 15, 30],
     [52, 5, 15, 30, 2],
     [53.1, 5.7, 15, 30, 2.4],
-    ['#VALUE!', 5.7, 'X', 30, 2.4], // error here conflicts with SUMIF
+    [52.1, 5.7, '14', 30, 2.4],
+    [38.1, 5.7, 'X', 30, 2.4], // error if entered in formula, but not in cell
+    [38.1, 5.7, null, 30, 2.4],
+    [38.1, 5.7, false, 30, 2.4],
+    [39.1, 5.7, true, 30, 2.4],
 ];
diff --git a/tests/data/Calculation/MathTrig/SUMLITERALS.php b/tests/data/Calculation/MathTrig/SUMLITERALS.php
new file mode 100644
index 00000000..fd184ebd
--- /dev/null
+++ b/tests/data/Calculation/MathTrig/SUMLITERALS.php
@@ -0,0 +1,12 @@
+<?php
+
+return [
+    [50, '5, 15, 30'],
+    [52, '5, 15, 30, 2'],
+    [53.1, '5.7, 15, 30, 2.4'],
+    [52.1, '5.7, "14", 30, 2.4'],
+    ['#VALUE!', '5.7, "X", 30, 2.4'], // error if entered in formula, but not in cell
+    [38.1, '5.7, , 30, 2.4'],
+    [38.1, '5.7, false, 30, 2.4'],
+    [39.1, '5.7, true, 30, 2.4'],
+];