diff --git a/phpBB/includes/functions_upload.php b/phpBB/includes/functions_upload.php
index c640865212..fb153a9e0c 100644
--- a/phpBB/includes/functions_upload.php
+++ b/phpBB/includes/functions_upload.php
@@ -52,11 +52,17 @@ class filespec
 	 */
 	protected $plupload;
 
+	/**
+	 * phpBB Mimetype guesser
+	 * @var \phpbb\mimetype\guesser
+	 */
+	protected $mimetype_guesser;
+
 	/**
 	* File Class
 	* @access private
 	*/
-	function filespec($upload_ary, $upload_namespace, \phpbb\plupload\plupload $plupload = null)
+	function filespec($upload_ary, $upload_namespace, \phpbb\mimetype\guesser $mimetype_guesser = null, \phpbb\plupload\plupload $plupload = null)
 	{
 		if (!isset($upload_ary))
 		{
@@ -90,6 +96,7 @@ class filespec
 		$this->local = (isset($upload_ary['local_mode'])) ? true : false;
 		$this->upload = $upload_namespace;
 		$this->plupload = $plupload;
+		$this->mimetype_guesser = $mimetype_guesser;
 	}
 
 	/**
@@ -215,25 +222,22 @@ class filespec
 	}
 
 	/**
-	* Get mimetype. Utilize mime_content_type if the function exist.
-	* Not used at the moment...
+	* Get mimetype
+	*
 	*/
 	function get_mimetype($filename)
 	{
-		$mimetype = '';
-
-		if (function_exists('mime_content_type'))
+		if ($this->mimetype_guesser !== null)
 		{
-			$mimetype = mime_content_type($filename);
+			$mimetype = $this->mimetype_guesser->guess($filename);
+
+			if ($mimetype !== 'application/octet-stream')
+			{
+				$this->mimetype = $mimetype;
+			}
 		}
 
-		// Some browsers choke on a mimetype of application/octet-stream
-		if (!$mimetype || $mimetype == 'application/octet-stream')
-		{
-			$mimetype = 'application/octetstream';
-		}
-
-		return $mimetype;
+		return $this->mimetype;
 	}
 
 	/**
@@ -372,6 +376,9 @@ class filespec
 		// Try to get real filesize from destination folder
 		$this->filesize = (@filesize($this->destination_file)) ? @filesize($this->destination_file) : $this->filesize;
 
+		// Get mimetype of supplied file
+		$this->mimetype = $this->get_mimetype($this->destination_file);
+
 		if ($this->is_image() && !$skip_image_check)
 		{
 			$this->width = $this->height = 0;
@@ -580,7 +587,7 @@ class fileupload
 	* @return object $file Object "filespec" is returned, all further operations can be done with this object
 	* @access public
 	*/
-	function form_upload($form_name, \phpbb\plupload\plupload $plupload = null)
+	function form_upload($form_name, \phpbb\mimetype\guesser $mimetype_guesser = null, \phpbb\plupload\plupload $plupload = null)
 	{
 		global $user, $request;
 
@@ -596,7 +603,7 @@ class fileupload
 			}
 		}
 
-		$file = new filespec($upload, $this, $plupload);
+		$file = new filespec($upload, $this, $mimetype_guesser, $plupload);
 
 		if ($file->init_error)
 		{
@@ -656,7 +663,7 @@ class fileupload
 	/**
 	* Move file from another location to phpBB
 	*/
-	function local_upload($source_file, $filedata = false)
+	function local_upload($source_file, $filedata = false, \phpbb\mimetype\guesser $mimetype_guesser = null)
 	{
 		global $user, $request;
 
@@ -670,19 +677,6 @@ class fileupload
 			$upload['name'] = utf8_basename($source_file);
 			$upload['size'] = 0;
 			$mimetype = '';
-
-			if (function_exists('mime_content_type'))
-			{
-				$mimetype = mime_content_type($source_file);
-			}
-
-			// Some browsers choke on a mimetype of application/octet-stream
-			if (!$mimetype || $mimetype == 'application/octet-stream')
-			{
-				$mimetype = 'application/octetstream';
-			}
-
-			$upload['type'] = $mimetype;
 		}
 		else
 		{
@@ -691,7 +685,7 @@ class fileupload
 			$upload['type'] = $filedata['type'];
 		}
 
-		$file = new filespec($upload, $this);
+		$file = new filespec($upload, $this, $mimetype_guesser);
 
 		if ($file->init_error)
 		{
@@ -749,7 +743,7 @@ class fileupload
 	* @return object $file Object "filespec" is returned, all further operations can be done with this object
 	* @access public
 	*/
-	function remote_upload($upload_url)
+	function remote_upload($upload_url, \phpbb\mimetype\guesser $mimetype_guesser = null)
 	{
 		global $user, $phpbb_root_path;
 
@@ -904,7 +898,7 @@ class fileupload
 
 		$upload_ary['tmp_name'] = $filename;
 
-		$file = new filespec($upload_ary, $this);
+		$file = new filespec($upload_ary, $this, $mimetype_guesser);
 		$this->common_checks($file);
 
 		return $file;
diff --git a/tests/upload/filespec_test.php b/tests/upload/filespec_test.php
index 5e333213f4..d8fa82e2b5 100644
--- a/tests/upload/filespec_test.php
+++ b/tests/upload/filespec_test.php
@@ -65,6 +65,16 @@ class phpbb_filespec_test extends phpbb_test_case
 				copy($fileinfo->getPathname(), $this->path . 'copies/' . $fileinfo->getFilename() . '_copy_2');
 			}
 		}
+
+		$guessers = array(
+			new \Symfony\Component\HttpFoundation\File\MimeType\FileinfoMimeTypeGuesser(),
+			new \Symfony\Component\HttpFoundation\File\MimeType\FileBinaryMimeTypeGuesser(),
+			new \phpbb\mimetype\content_guesser(),
+			new \phpbb\mimetype\extension_guesser(),
+		);
+		$guessers[2]->set_priority(-2);
+		$guessers[3]->set_priority(-2);
+		$this->mimetype_guesser = new \phpbb\mimetype\guesser($guessers);
 	}
 
 	private function get_filespec($override = array())
@@ -78,7 +88,7 @@ class phpbb_filespec_test extends phpbb_test_case
 			'error' => '',
 		);
 
-		return new filespec(array_merge($upload_ary, $override), null);
+		return new filespec(array_merge($upload_ary, $override), null, $this->mimetype_guesser);
 	}
 
 	protected function tearDown()
@@ -222,6 +232,9 @@ class phpbb_filespec_test extends phpbb_test_case
 			array('png', 'image/png', true),
 			array('tif', 'image/tif', true),
 			array('txt', 'text/plain', false),
+			array('jpg', 'application/octet-stream', false),
+			array('gif', 'application/octetstream', false),
+			array('png', 'application/mime', false),
 		);
 	}
 
@@ -234,6 +247,30 @@ class phpbb_filespec_test extends phpbb_test_case
 		$this->assertEquals($expected, $filespec->is_image());
 	}
 
+	public function is_image_get_mimetype()
+	{
+		return array(
+			array('gif', 'image/gif', true),
+			array('jpg', 'image/jpg', true),
+			array('png', 'image/png', true),
+			array('tif', 'image/tif', true),
+			array('txt', 'text/plain', false),
+			array('jpg', 'application/octet-stream', true),
+			array('gif', 'application/octetstream', true),
+			array('png', 'application/mime', true),
+		);
+	}
+
+	/**
+	 * @dataProvider is_image_get_mimetype
+	 */
+	public function test_is_image_get_mimetype($filename, $mimetype, $expected)
+	{
+		$filespec = $this->get_filespec(array('tmp_name' => $this->path . $filename, 'type' => $mimetype));
+		$filespec->get_mimetype($this->path . $filename);
+		$this->assertEquals($expected, $filespec->is_image());
+	}
+
 	public function move_file_variables()
 	{
 		return array(