diff --git a/config_defaults_inc.php b/config_defaults_inc.php
index ef5cd8c2c7..a894e3b658 100644
--- a/config_defaults_inc.php
+++ b/config_defaults_inc.php
@@ -3486,6 +3486,22 @@
 	'zip'	=> 'zip.gif',
 	'?'	=> 'generic.gif' );
 
+/**
+ * 
+ * Content types which will be overriden when downloading files
+ * 
+ * @global array $g_file_download_content_type_overrides
+ */
+$g_file_download_content_type_overrides = array (
+	'docx' => 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+	'dotx' => 'application/vnd.openxmlformats-officedocument.wordprocessingml.template',
+	'pptx' => 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
+	'ppsx' => 'application/vnd.openxmlformats-officedocument.presentationml.slideshow',
+	'potx' => 'application/vnd.openxmlformats-officedocument.presentationml.template',
+	'xlsx' => 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+	'xltx' => 'application/vnd.openxmlformats-officedocument.spreadsheetml.template'
+);
+
 /**
  * Icon associative arrays
  * Status to icon mapping
diff --git a/core/file_api.php b/core/file_api.php
index 51e0e69d88..fc44dd7d11 100644
--- a/core/file_api.php
+++ b/core/file_api.php
@@ -1063,3 +1063,18 @@ function file_copy_attachments( $p_source_bug_id, $p_dest_bug_id ) {
         db_query_bound( $query, Array( $p_dest_bug_id, $t_bug_file['title'], $t_bug_file['description'], $t_new_diskfile_name, $t_new_file_name, $t_bug_file['folder'], $t_bug_file['filesize'], $t_bug_file['file_type'], $t_bug_file['date_added'], $t_bug_file['content'] ) );
     }
 }
+
+/**
+ * Returns a possibly override content type for a file name
+ * 
+ * @param string $p_filename the filename of the file which will be downloaded
+ * @return string the content type, or empty if it should not be overriden
+ */
+function file_get_content_type_override( $p_filename ) {
+	
+	global $g_file_download_content_type_overrides;
+	
+	$t_extension = pathinfo( $p_filename, PATHINFO_EXTENSION );
+	
+	return $g_file_download_content_type_overrides[$t_extension];
+}
\ No newline at end of file
diff --git a/file_download.php b/file_download.php
index b72cedce97..f59ae4ce52 100644
--- a/file_download.php
+++ b/file_download.php
@@ -167,6 +167,8 @@
 
 $t_content_type = $v_file_type;
 
+$t_content_type_override = file_get_content_type_override ( $t_filename );
+
 # dump file content to the connection.
 switch ( config_get( 'file_upload_method' ) ) {
 	case DISK:
@@ -180,6 +182,9 @@
 					$t_content_type = $t_file_info_type;
 				}
 			}
+			
+			if ( $t_content_type_override )
+				$t_content_type = $t_content_type_override;
 
 			header( 'Content-Type: ' . $t_content_type );
 			if ( config_get( 'file_download_xsendfile_enabled' ) ) {
@@ -206,6 +211,9 @@
 				$t_content_type = $t_file_info_type;
 			}
 		}
+		
+		if ( $t_content_type_override )
+			$t_content_type = $t_content_type_override;
 
 		header( 'Content-Type: ' . $t_content_type );
 		readfile( $t_local_disk_file );
@@ -218,6 +226,9 @@
 				$t_content_type = $t_file_info_type;
 			}
 		}
+		
+		if ( $t_content_type_override )
+			$t_content_type = $t_content_type_override;
 
 		header( 'Content-Type: ' . $t_content_type );
 		echo $v_content;