diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 4423b594..d56cf27d 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -5660,16 +5660,6 @@ parameters:
 			count: 2
 			path: src/PhpSpreadsheet/Writer/Xlsx/Comments.php
 
-		-
-			message: "#^Parameter \\#1 \\$arr1 of function array_diff expects array, array\\|null given\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php
-
-		-
-			message: "#^Cannot access offset 2 on array\\|false\\.$#"
-			count: 1
-			path: src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php
-
 		-
 			message: "#^Parameter \\#2 \\$content of method XMLWriter\\:\\:writeElement\\(\\) expects string\\|null, int given\\.$#"
 			count: 1
diff --git a/src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php b/src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php
index 2cff1a8f..e5cf65c9 100644
--- a/src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php
+++ b/src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php
@@ -141,7 +141,7 @@ class ContentTypes extends WriterPart
         if ($spreadsheet->hasRibbonBinObjects()) {
             // Some additional objects in the ribbon ?
             // we need to write "Extension" but not already write for media content
-            $tabRibbonTypes = array_diff($spreadsheet->getRibbonBinObjects('types'), array_keys($aMediaContentTypes));
+            $tabRibbonTypes = array_diff($spreadsheet->getRibbonBinObjects('types') ?? [], array_keys($aMediaContentTypes));
             foreach ($tabRibbonTypes as $aRibbonType) {
                 $mimeType = 'image/.' . $aRibbonType; //we wrote $mimeType like customUI Editor
                 $this->writeDefaultContentType($objWriter, $aRibbonType, $mimeType);
@@ -192,7 +192,7 @@ class ContentTypes extends WriterPart
         if (File::fileExists($pFile)) {
             $image = getimagesize($pFile);
 
-            return image_type_to_mime_type($image[2]);
+            return image_type_to_mime_type((is_array($image) && count($image) >= 3) ? $image[2] : 0);
         }
 
         throw new WriterException("File $pFile does not exist");
diff --git a/tests/PhpSpreadsheetTests/Writer/Xlsx/WmfTest.php b/tests/PhpSpreadsheetTests/Writer/Xlsx/WmfTest.php
new file mode 100644
index 00000000..35ae742c
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Writer/Xlsx/WmfTest.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
+
+use PhpOffice\PhpSpreadsheet\Reader\Xlsx;
+use PhpOffice\PhpSpreadsheetTests\Functional\AbstractFunctional;
+
+class WmfTest extends AbstractFunctional
+{
+    /**
+     * Test save and load XLSX file with wmf image.
+     */
+    public function testWmf(): void
+    {
+        // Read spreadsheet from file
+        $inputFilename = 'tests/data/Writer/XLSX/wmffile.xlsx';
+        $reader = new Xlsx();
+        $spreadsheet = $reader->load($inputFilename);
+        $drawings = $spreadsheet->getActiveSheet()->getDrawingCollection();
+        self::assertCount(1, $drawings);
+        $drawing = $drawings[0];
+        self::assertSame('wmf', $drawing->getExtension());
+
+        // Save spreadsheet to file and read it back
+        $reloadedSpreadsheet = $this->writeAndReload($spreadsheet, 'Xlsx');
+        $drawings = $reloadedSpreadsheet->getActiveSheet()->getDrawingCollection();
+        self::assertCount(1, $drawings);
+        $drawing = $drawings[0];
+        self::assertSame('wmf', $drawing->getExtension());
+
+        $spreadsheet->disconnectWorksheets();
+        $reloadedSpreadsheet->disconnectWorksheets();
+    }
+}
diff --git a/tests/data/Writer/XLSX/wmffile.xlsx b/tests/data/Writer/XLSX/wmffile.xlsx
new file mode 100644
index 00000000..64df51aa
Binary files /dev/null and b/tests/data/Writer/XLSX/wmffile.xlsx differ