diff --git a/Classes/PHPExcel.php b/Classes/PHPExcel.php
index bc85208..df111d4 100644
--- a/Classes/PHPExcel.php
+++ b/Classes/PHPExcel.php
@@ -244,6 +244,12 @@ class PHPExcel
 		} else {
 			array_splice($this->_workSheetCollection, $pIndex, 1);
 		}
+		// Adjust active sheet index if necessary
+		if (($this->_activeSheetIndex >= $pIndex) &&
+			($pIndex > count($this->_workSheetCollection) - 1)) {
+			--$this->_activeSheetIndex;
+		}
+
 	}
 
 	/**
diff --git a/Classes/PHPExcel/Cell/DataType.php b/Classes/PHPExcel/Cell/DataType.php
index 775d99d..e2410b3 100644
--- a/Classes/PHPExcel/Cell/DataType.php
+++ b/Classes/PHPExcel/Cell/DataType.php
@@ -41,7 +41,7 @@ class PHPExcel_Cell_DataType
 	const TYPE_FORMULA		= 'f';
 	const TYPE_NUMERIC		= 'n';
 	const TYPE_BOOL			= 'b';
-    const TYPE_NULL			= 's';
+    const TYPE_NULL			= 'null';
     const TYPE_INLINE		= 'inlineStr';
 	const TYPE_ERROR		= 'e';
 
diff --git a/Classes/PHPExcel/Reader/CSV.php b/Classes/PHPExcel/Reader/CSV.php
index ee342ac..dfc0280 100644
--- a/Classes/PHPExcel/Reader/CSV.php
+++ b/Classes/PHPExcel/Reader/CSV.php
@@ -217,7 +217,7 @@ class PHPExcel_Reader_CSV implements PHPExcel_Reader_IReader
 		}
 		$objPHPExcel->setActiveSheetIndex( $this->_sheetIndex );
 
-		$lineEnding = ini_set('auto_detect_line_endings');
+		$lineEnding = ini_get('auto_detect_line_endings');
 		ini_set('auto_detect_line_endings', true);
 
 		// Open file
diff --git a/Classes/PHPExcel/Reader/Excel2003XML.php b/Classes/PHPExcel/Reader/Excel2003XML.php
index 6e437de..608bfe2 100644
--- a/Classes/PHPExcel/Reader/Excel2003XML.php
+++ b/Classes/PHPExcel/Reader/Excel2003XML.php
@@ -651,7 +651,7 @@ class PHPExcel_Reader_Excel2003XML implements PHPExcel_Reader_IReader
 									const TYPE_FORMULA		= 'f';
 									const TYPE_NUMERIC		= 'n';
 									const TYPE_BOOL			= 'b';
-								    const TYPE_NULL			= 's';
+								    const TYPE_NULL			= 'null';
 								    const TYPE_INLINE		= 'inlineStr';
 									const TYPE_ERROR		= 'e';
 									*/
diff --git a/Classes/PHPExcel/Writer/Excel5/Worksheet.php b/Classes/PHPExcel/Writer/Excel5/Worksheet.php
index 8efe315..baa72a4 100644
--- a/Classes/PHPExcel/Writer/Excel5/Worksheet.php
+++ b/Classes/PHPExcel/Writer/Excel5/Worksheet.php
@@ -410,6 +410,7 @@ class PHPExcel_Writer_Excel5_Worksheet extends PHPExcel_Writer_Excel5_BIFFwriter
 			} else {
 				switch ($cell->getDatatype()) {
 					case PHPExcel_Cell_DataType::TYPE_STRING:
+					case PHPExcel_Cell_DataType::TYPE_NULL:
 						if ($cVal === '' || $cVal === null) {
 							$this->_writeBlank($row, $column, $xfIndex);
 						} else {
diff --git a/Documentation/Functionality Cross-Reference.xls b/Documentation/Functionality Cross-Reference.xls
index e25107a..c70fa93 100644
Binary files a/Documentation/Functionality Cross-Reference.xls and b/Documentation/Functionality Cross-Reference.xls differ
diff --git a/changelog.txt b/changelog.txt
index 3015f5c..cbacf02 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -40,9 +40,11 @@ Fixed in SVN:
                      auto_detect_line_endings now set in CSV reader
 - Bugfix:   (MBaker) Work item 16212 - $arguments improperly used in CachedObjectStorage/PHPTemp.php
 - Bugfix:   (MBaker) Work item 16643 - Bug In Cache System (cell reference when throwing caching errors)
+- Bugfix:   (MBaker) Work item 16895 - PHP Invalid index notice on writing excel file when active sheet has been deleted
 - General:  (MBaker) Work item 15405 - Two easy to fix Issues concerning PHPExcel_Token_Stack (l10n/UC)
 - General:  (MBaker) Work item 15461 - Locale file paths not fit for windows
 - General:  (MBaker) Work item 16643 - Add file directory as a cache option for cache_to_discISAM
+- General:  (MBaker) Work item 16923 - Datatype.php & constant TYPE_NULL
 
 
 2011-02-27 (v1.7.6):