diff --git a/src/PhpSpreadsheet/ReferenceHelper.php b/src/PhpSpreadsheet/ReferenceHelper.php
index 23f5ffef..f4073a5f 100644
--- a/src/PhpSpreadsheet/ReferenceHelper.php
+++ b/src/PhpSpreadsheet/ReferenceHelper.php
@@ -547,7 +547,7 @@ class ReferenceHelper
         $autoFilterRange = $autoFilter->getRange();
         if (!empty($autoFilterRange)) {
             if ($pNumCols != 0) {
-                $autoFilterColumns = array_keys($autoFilter->getColumns());
+                $autoFilterColumns = $autoFilter->getColumns();
                 if (count($autoFilterColumns) > 0) {
                     sscanf($pBefore, '%[A-Z]%d', $column, $row);
                     $columnIndex = Cell::columnIndexFromString($column);
@@ -559,7 +559,7 @@ class ReferenceHelper
                             $deleteColumn = $columnIndex + $pNumCols - 1;
                             $deleteCount = abs($pNumCols);
                             for ($i = 1; $i <= $deleteCount; ++$i) {
-                                if (in_array(Cell::stringFromColumnIndex($deleteColumn), $autoFilterColumns)) {
+                                if (isset($autoFilterColumns[Cell::stringFromColumnIndex($deleteColumn)])) {
                                     $autoFilter->clearColumn(Cell::stringFromColumnIndex($deleteColumn));
                                 }
                                 ++$deleteColumn;
diff --git a/src/PhpSpreadsheet/Writer/Xls/Worksheet.php b/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
index 333fc540..7b050290 100644
--- a/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
+++ b/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
@@ -518,8 +518,10 @@ class Worksheet extends BIFFwriter
                 foreach ($conditionalStyles as $conditional) {
                     if ($conditional->getConditionType() == \PhpOffice\PhpSpreadsheet\Style\Conditional::CONDITION_EXPRESSION
                         || $conditional->getConditionType() == \PhpOffice\PhpSpreadsheet\Style\Conditional::CONDITION_CELLIS) {
-                        if (!in_array($conditional->getHashCode(), $arrConditional)) {
-                            $arrConditional[] = $conditional->getHashCode();
+                        if (!isset($arrConditional[$conditional->getHashCode()])) {
+                            // This hash code has been handled
+                            $arrConditional[$conditional->getHashCode()] = true;
+
                             // Write CFRULE record
                             $this->writeCFRule($conditional);
                         }