diff --git a/phpBB/phpbb/mimetype/content_guesser.php b/phpBB/phpbb/mimetype/content_guesser.php
index 6bdd410af4..6326bf73fa 100644
--- a/phpBB/phpbb/mimetype/content_guesser.php
+++ b/phpBB/phpbb/mimetype/content_guesser.php
@@ -492,7 +492,7 @@ class content_guesser
 	*
 	* @return string Guess for mimetype of file
 	*/
-	public function guess($file)
+	public function guess($file, $file_name = '')
 	{
 		$mimetype = null;
 		if (function_exists('mime_content_type'))
@@ -501,14 +501,22 @@ class content_guesser
 		}
 		else
 		{
-			$mimetype = $this->map_extension_to_type($file);
+			$file_name = (empty($file_name)) ? $file : $file_name;
+			$mimetype = $this->map_extension_to_type($file_name);
 		}
 		return $mimetype;
 	}
 
-	protected function map_extension_to_type($file)
+	/**
+	* Map extension of supplied file_name to mime type
+	*
+	* @param string $file_name Path to file or filename
+	*
+	* @return string|null Mimetype if known or null if not
+	*/
+	protected function map_extension_to_type($file_name)
 	{
-		$extension = pathinfo($file, PATHINFO_EXTENSION);
+		$extension = pathinfo($file_name, PATHINFO_EXTENSION);
 
 		if (isset($this->extension_map[$extension]))
 		{
diff --git a/phpBB/phpbb/mimetype/guesser.php b/phpBB/phpbb/mimetype/guesser.php
index 5ae094cd63..231b75f604 100644
--- a/phpBB/phpbb/mimetype/guesser.php
+++ b/phpBB/phpbb/mimetype/guesser.php
@@ -77,7 +77,7 @@ class guesser
 	*
 	* @return string Guess for mimetype of file
 	*/
-	public function guess($file)
+	public function guess($file, $file_name = '')
 	{
 		if (!is_file($file))
 		{
@@ -91,7 +91,7 @@ class guesser
 
 		foreach ($this->guessers as $guesser)
 		{
-			$mimetype = $guesser->guess($file);
+			$mimetype = $guesser->guess($file, $file_name);
 
 			// Try to guess something that is not the fallback application/octet-stream
 			if ($mimetype !== null && $mimetype !== 'application/octet-stream')
diff --git a/phpBB/phpbb/plupload/plupload.php b/phpBB/phpbb/plupload/plupload.php
index 29a4aff39b..dedc3cbcd4 100644
--- a/phpBB/phpbb/plupload/plupload.php
+++ b/phpBB/phpbb/plupload/plupload.php
@@ -135,7 +135,7 @@ class plupload
 				'tmp_name' => $file_path,
 				'name' => $this->request->variable('real_filename', ''),
 				'size' => filesize($file_path),
-				'type' => $this->mimetype_guesser->guess($file_path),
+				'type' => $this->mimetype_guesser->guess($file_path, $file_name),
 			);
 		}
 		else
diff --git a/tests/mimetype/guesser_test.php b/tests/mimetype/guesser_test.php
index 6484606210..9d4d965d63 100644
--- a/tests/mimetype/guesser_test.php
+++ b/tests/mimetype/guesser_test.php
@@ -119,8 +119,9 @@ class guesser_test extends \phpbb_test_case
 	public function test_content_guesser($expected, $overload = false)
 	{
 		self::$function_exists = ($overload) ? false : true;
-		$guesser = new \phpbb\mimetype\guesser(array(new \phpbb\mimetype\content_guesser($this->phpbb_root_path, new \phpbb\php\ini)));
+		$guesser = new \phpbb\mimetype\guesser(array(new \phpbb\mimetype\content_guesser));
 		$this->assertEquals($expected[0], $guesser->guess($this->jpg_file));
+		$this->assertEquals($expected[1], $guesser->guess($this->jpg_file, $this->jpg_file . '.jpg'));
 		@copy($this->jpg_file, $this->jpg_file . '.jpg');
 		$this->assertEquals($expected[1], $guesser->guess($this->jpg_file . '.jpg'));
 		@unlink($this->jpg_file . '.jpg');