diff --git a/Classes/PHPExcel/Reader/Excel5.php b/Classes/PHPExcel/Reader/Excel5.php
index 9b122e4ff..95dc57823 100644
--- a/Classes/PHPExcel/Reader/Excel5.php
+++ b/Classes/PHPExcel/Reader/Excel5.php
@@ -3609,7 +3609,7 @@ private function readRow()
             // bit: 27-16; mask: 0x0FFF0000; only applies when hasExplicitFormat = 1; index to XF record
             $xfIndex = (0x0FFF0000 & self::getInt4d($recordData, 12)) >> 16;
 
-            if ($hasExplicitFormat) {
+            if ($hasExplicitFormat && isset($this->mapCellXfIndex[$xfIndex])) {
                 $this->phpSheet->getRowDimension($r + 1)->setXfIndex($this->mapCellXfIndex[$xfIndex]);
             }
         }