diff --git a/PHPExcel/PHPExcel/Worksheet/AutoFilter.php b/PHPExcel/PHPExcel/Worksheet/AutoFilter.php
index 6ec8a44..1bc312b 100755
--- a/PHPExcel/PHPExcel/Worksheet/AutoFilter.php
+++ b/PHPExcel/PHPExcel/Worksheet/AutoFilter.php
@@ -717,7 +717,7 @@ class PHPExcel_Worksheet_AutoFilter
                             );
                         } else {
                             //    Date based
-                            if ($dynamicRuleType{0} == 'M' || $dynamicRuleType{0} == 'Q') {
+                            if ($dynamicRuleType[0] == 'M' || $dynamicRuleType[0] == 'Q') {
                                 //    Month or Quarter
                                 sscanf($dynamicRuleType, '%[A-Z]%d', $periodType, $period);
                                 if ($periodType == 'M') {