diff --git a/PHPExcel/PHPExcel/Calculation.php b/PHPExcel/PHPExcel/Calculation.php
index 88bcf48..0469d1d 100755
--- a/PHPExcel/PHPExcel/Calculation.php
+++ b/PHPExcel/PHPExcel/Calculation.php
@@ -2761,7 +2761,7 @@ class PHPExcel_Calculation {
 			$opCharacter = $formula[$index];	//	Get the first character of the value at the current index position
 //echo 'Initial character of expression block is '.$opCharacter,PHP_EOL;
 			if ((isset(self::$_comparisonOperators[$opCharacter])) && (strlen($formula) > $index) && (isset(self::$_comparisonOperators[$formula[$index+1]]))) {
-				$opCharacter .= $formula{++$index};
+				$opCharacter .= $formula[++$index];
 //echo 'Initial character of expression block is comparison operator '.$opCharacter.PHP_EOL;
 			}