diff --git a/Classes/PHPExcel/Writer/Excel5/Parser.php b/Classes/PHPExcel/Writer/Excel5/Parser.php
index 7bdc1c0b..bc6ddb13 100644
--- a/Classes/PHPExcel/Writer/Excel5/Parser.php
+++ b/Classes/PHPExcel/Writer/Excel5/Parser.php
@@ -1430,6 +1430,7 @@ class PHPExcel_Writer_Excel5_Parser
 		{
 		    if($this->_lookahead == '%'){
 		        $result = $this->_createTree('ptgPercent', $this->_current_token, '');
+                $this->_advance();  // Skip the percentage operator once we've pre-built that tree
 		    } else {
 		        $result = $this->_createTree($this->_current_token, '', '');
 		    }
diff --git a/changelog.txt b/changelog.txt
index 13f434e4..8e4a5f6e 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -31,6 +31,7 @@ Planned for v1.8.1
 - Bugfix:   (MBaker)          Work Item CP18105 - Loading an Excel 2007 spreadsheet throws an "Autofilter must be set on a range of cells" exception
 - Bugfix:   (MBaker)                            - Fix to autoloader registration for backward compatibility with PHP 5.2.0 not accepting the prepend flag
 - Bugfix:   (MBaker)          Work Item GH-384  - DOM loadHTMLFile() failing with options flags when using PHP < 5.4.0
+- Bugfix:   (MBaker)                            - Fix for percentage operator in formulae for BIFF Writer
 - General:  (MBaker)                            - Small performance improvement for autosize columns
 - General:  (frost-nzcr4)     Work Item GH-379  - Change the getter/setter for zeroHeight to camel case
 - Feature:  (WiktrzGE)        Work Item GH-404  - Methods to manage most of the existing options for Chart Axis, Major Grid-lines and Minor Grid-lines