diff --git a/src/Http/FileUpload.php b/src/Http/FileUpload.php
index 52982b6c..cefbf8d1 100644
--- a/src/Http/FileUpload.php
+++ b/src/Http/FileUpload.php
@@ -41,6 +41,9 @@ final class FileUpload
 	/** @var string|false|null */
 	private $type;
 
+	/** @var string|false|null */
+	private $extension;
+
 	/** @var int */
 	private $size;
 
@@ -98,9 +101,9 @@ public function getSanitizedName(): string
 		$name = str_replace(['-.', '.-'], '.', $name);
 		$name = trim($name, '.-');
 		$name = $name === '' ? 'unknown' : $name;
-		if ($this->isImage()) {
+		if ($ext = $this->getSuggestedExtension()) {
 			$name = preg_replace('#\.[^.]+$#D', '', $name);
-			$name .= '.' . ($this->getImageFileExtension() ?? 'unknown');
+			$name .= '.' . $ext;
 		}
 
 		return $name;
@@ -134,6 +137,27 @@ public function getContentType(): ?string
 	}
 
 
+	/**
+	 * Returns the appropriate file extension (without the period) corresponding to the detected MIME type. Requires the PHP extension fileinfo.
+	 */
+	public function getSuggestedExtension(): ?string
+	{
+		if ($this->isOk() && $this->extension === null) {
+			$exts = finfo_file(finfo_open(FILEINFO_EXTENSION), $this->tmpName);
+			if ($exts && $exts !== '???') {
+				return $this->extension = preg_replace('~[/,].*~', '', $exts);
+			}
+			[, , $type] = @getimagesize($this->tmpName); // @ - files smaller than 12 bytes causes read error
+			if ($type) {
+				return $this->extension = image_type_to_extension($type, false);
+			}
+			$this->extension = false;
+		}
+
+		return $this->extension ?: null;
+	}
+
+
 	/**
 	 * Returns the size of the uploaded file in bytes.
 	 */
@@ -252,12 +276,11 @@ public function getImageSize(): ?array
 
 	/**
 	 * Returns image file extension based on detected content type (without dot).
+	 * @deprecated use getSuggestedExtension()
 	 */
 	public function getImageFileExtension(): ?string
 	{
-		return $this->isImage()
-			? explode('/', $this->getContentType())[1]
-			: null;
+		return $this->getSuggestedExtension();
 	}
 
 
diff --git a/tests/Http/FileUpload.basic.phpt b/tests/Http/FileUpload.basic.phpt
index 573568af..505774dc 100644
--- a/tests/Http/FileUpload.basic.phpt
+++ b/tests/Http/FileUpload.basic.phpt
@@ -33,7 +33,7 @@ test('', function () {
 	Assert::true($upload->isOk());
 	Assert::true($upload->hasFile());
 	Assert::false($upload->isImage());
-	Assert::null($upload->getImageFileExtension());
+	Assert::null($upload->getSuggestedExtension());
 	Assert::same(file_get_contents(__DIR__ . '/files/file.txt'), $upload->getContents());
 });
 
@@ -51,7 +51,7 @@ test('', function () {
 	Assert::same('image.png', $upload->getSanitizedName());
 	Assert::same('../.image.png', $upload->getUntrustedFullPath());
 	Assert::same('image/png', $upload->getContentType());
-	Assert::same('png', $upload->getImageFileExtension());
+	Assert::same('png', $upload->getSuggestedExtension());
 	Assert::same([108, 46], $upload->getImageSize());
 	Assert::true($upload->isImage());
 });
@@ -68,6 +68,7 @@ test('', function () {
 
 	Assert::false($upload->isOk());
 	Assert::false($upload->hasFile());
+	Assert::null($upload->getContentType());
 	Assert::false($upload->isImage());
-	Assert::null($upload->getImageFileExtension());
+	Assert::null($upload->getSuggestedExtension());
 });
diff --git a/tests/Http/FileUpload.getSanitizedName.phpt b/tests/Http/FileUpload.getSanitizedName.phpt
index 825c147f..0b0c6cce 100644
--- a/tests/Http/FileUpload.getSanitizedName.phpt
+++ b/tests/Http/FileUpload.getSanitizedName.phpt
@@ -43,7 +43,7 @@ Assert::with(new FileUpload([]), function () {
 
 
 Assert::with(new FileUpload([]), function () {
-	$this->type = 'image/jpeg';
+	$this->extension = 'jpeg';
 
 	$this->name = '';
 	Assert::same('unknown.jpeg', $this->getSanitizedName());