diff --git a/README.md b/README.md
index cad03d8..f59691a 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ your concerns remain unanswered.
 * Serve a complete file.
 * Serve a single byte range of a file.
 * Serve multiple byte ranges of a file.
+* Set a custom mimetype.
 
 ## Requirements
 
diff --git a/src/FileStreamer.php b/src/FileStreamer.php
index e4a39ad..28f3b8a 100644
--- a/src/FileStreamer.php
+++ b/src/FileStreamer.php
@@ -59,6 +59,10 @@ class FileStreamer
      * @var false|resource Handle to the file to serve.
      */
     private $filePointer;
+    /**
+     * @var string|null If not null, it defines type mimetype of the file to download.
+     */
+    private ?string $mimeType = null;
 
     /**
      * Class Constructor.
@@ -90,6 +94,20 @@ public function setInline(bool $inline = true): void
         $this->inline = $inline;
     }
 
+    /**
+     * Set the mimetype of to file to serve.
+     *
+     * When not null, it overrides getting the mimetype automatically when the headers are sent.
+     *
+     * @param   string|null  $mimeType  the mimetype of the file to serve.
+     *
+     * @return void
+     */
+    public function setMimeType(?string $mimeType): void
+    {
+        $this->mimeType = $mimeType;
+    }
+
     /**
      * Start serving the file.
      *
@@ -231,8 +249,11 @@ private function sendHeaders(int $type): void
         // Get file mimetype.
         $filePath = $this->fileInfo->getPathname();
         $fileSize = $this->fileInfo->getSize();
-        $fileInfo = new finfo();
-        $mimeType = @$fileInfo->file($filePath, FILEINFO_MIME_TYPE);
+        $mimeType = $this->mimeType;
+        if (null === $mimeType) {
+            $fileInfo = new finfo();
+            $mimeType = @$fileInfo->file($filePath, FILEINFO_MIME_TYPE);
+        }
 
         // Caching headers as IE6 workaround.
         header('Pragma: public');
diff --git a/tests/FileStreamerTest.php b/tests/FileStreamerTest.php
index e54318b..b569420 100644
--- a/tests/FileStreamerTest.php
+++ b/tests/FileStreamerTest.php
@@ -243,6 +243,7 @@ public function testStartMultiRange(): void
 
     /**
      * Test if the correct data is being served when no range is requested.
+     * Also, it tests setting a custom Content-Type.
      *
      * @return void
      */
@@ -265,8 +266,10 @@ public function testStartNoRange(): void
         // Inline disposition Test.
         Output::reset();
         $mock->setInline(true);
+        $mock->setMimeType('digilive/test');
 
         $expectedHeaders = array_merge(self::defaultHeaders, ['Content-Disposition: inline']);
+        $expectedHeaders[4] = 'Content-Type: digilive/test';
 
         try {
             // Suppress warning or method will be aborted.