diff --git a/Classes/PHPExcel/Writer/CSV.php b/Classes/PHPExcel/Writer/CSV.php
index 2ff5b410..3979d609 100644
--- a/Classes/PHPExcel/Writer/CSV.php
+++ b/Classes/PHPExcel/Writer/CSV.php
@@ -102,8 +102,8 @@ class PHPExcel_Writer_CSV extends PHPExcel_Writer_Abstract implements PHPExcel_W
 		// Fetch sheet
 		$sheet = $this->_phpExcel->getSheet($this->_sheetIndex);
 
-		$saveDebugLog = PHPExcel_Calculation::getInstance()->writeDebugLog;
-		PHPExcel_Calculation::getInstance()->writeDebugLog = false;
+		$saveDebugLog = PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog;
+		PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog = FALSE;
 		$saveArrayReturnType = PHPExcel_Calculation::getArrayReturnType();
 		PHPExcel_Calculation::setArrayReturnType(PHPExcel_Calculation::RETURN_ARRAY_AS_VALUE);
 
@@ -139,7 +139,7 @@ class PHPExcel_Writer_CSV extends PHPExcel_Writer_Abstract implements PHPExcel_W
 		fclose($fileHandle);
 
 		PHPExcel_Calculation::setArrayReturnType($saveArrayReturnType);
-		PHPExcel_Calculation::getInstance()->writeDebugLog = $saveDebugLog;
+		PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog = $saveDebugLog;
 	}
 
 	/**
diff --git a/Classes/PHPExcel/Writer/Excel2007.php b/Classes/PHPExcel/Writer/Excel2007.php
index a74350ca..951b3397 100644
--- a/Classes/PHPExcel/Writer/Excel2007.php
+++ b/Classes/PHPExcel/Writer/Excel2007.php
@@ -179,8 +179,8 @@ class PHPExcel_Writer_Excel2007 extends PHPExcel_Writer_Abstract implements PHPE
 				}
 			}
 
-			$saveDebugLog = PHPExcel_Calculation::getInstance()->writeDebugLog;
-			PHPExcel_Calculation::getInstance()->writeDebugLog = false;
+			$saveDebugLog = PHPExcel_Calculation::getInstance($this->_spreadSheet)->writeDebugLog;
+			PHPExcel_Calculation::getInstance($this->_spreadSheet)->writeDebugLog = false;
 			$saveDateReturnType = PHPExcel_Calculation_Functions::getReturnDateType();
 			PHPExcel_Calculation_Functions::setReturnDateType(PHPExcel_Calculation_Functions::RETURNDATE_EXCEL);
 
@@ -341,7 +341,7 @@ class PHPExcel_Writer_Excel2007 extends PHPExcel_Writer_Abstract implements PHPE
 			}
 
 			PHPExcel_Calculation_Functions::setReturnDateType($saveDateReturnType);
-			PHPExcel_Calculation::getInstance()->writeDebugLog = $saveDebugLog;
+			PHPExcel_Calculation::getInstance($this->_spreadSheet)->writeDebugLog = $saveDebugLog;
 
 			// Close file
 			if ($objZip->close() === false) {
diff --git a/Classes/PHPExcel/Writer/Excel5.php b/Classes/PHPExcel/Writer/Excel5.php
index 459653c6..daa1d0fe 100644
--- a/Classes/PHPExcel/Writer/Excel5.php
+++ b/Classes/PHPExcel/Writer/Excel5.php
@@ -120,13 +120,13 @@ class PHPExcel_Writer_Excel5 extends PHPExcel_Writer_Abstract implements PHPExce
 		// garbage collect
 		$this->_phpExcel->garbageCollect();
 
-		$saveDebugLog = PHPExcel_Calculation::getInstance()->writeDebugLog;
-		PHPExcel_Calculation::getInstance()->writeDebugLog = false;
+		$saveDebugLog = PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog;
+		PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog = false;
 		$saveDateReturnType = PHPExcel_Calculation_Functions::getReturnDateType();
 		PHPExcel_Calculation_Functions::setReturnDateType(PHPExcel_Calculation_Functions::RETURNDATE_EXCEL);
 
 		// initialize colors array
-		$this->_colors          = array();
+		$this->_colors = array();
 
 		// Initialise workbook writer
 		$this->_writerWorkbook = new PHPExcel_Writer_Excel5_Workbook($this->_phpExcel,
@@ -226,7 +226,7 @@ class PHPExcel_Writer_Excel5 extends PHPExcel_Writer_Abstract implements PHPExce
 		$res = $root->save($pFilename);
 
 		PHPExcel_Calculation_Functions::setReturnDateType($saveDateReturnType);
-		PHPExcel_Calculation::getInstance()->writeDebugLog = $saveDebugLog;
+		PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog = $saveDebugLog;
 	}
 
 	/**
diff --git a/Classes/PHPExcel/Writer/HTML.php b/Classes/PHPExcel/Writer/HTML.php
index d07dbd2d..5aca92e9 100644
--- a/Classes/PHPExcel/Writer/HTML.php
+++ b/Classes/PHPExcel/Writer/HTML.php
@@ -152,8 +152,8 @@ class PHPExcel_Writer_HTML extends PHPExcel_Writer_Abstract implements PHPExcel_
 		// garbage collect
 		$this->_phpExcel->garbageCollect();
 
-		$saveDebugLog = PHPExcel_Calculation::getInstance()->writeDebugLog;
-		PHPExcel_Calculation::getInstance()->writeDebugLog = false;
+		$saveDebugLog = PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog;
+		PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog = false;
 		$saveArrayReturnType = PHPExcel_Calculation::getArrayReturnType();
 		PHPExcel_Calculation::setArrayReturnType(PHPExcel_Calculation::RETURN_ARRAY_AS_VALUE);
 
@@ -184,7 +184,7 @@ class PHPExcel_Writer_HTML extends PHPExcel_Writer_Abstract implements PHPExcel_
 		fclose($fileHandle);
 
 		PHPExcel_Calculation::setArrayReturnType($saveArrayReturnType);
-		PHPExcel_Calculation::getInstance()->writeDebugLog = $saveDebugLog;
+		PHPExcel_Calculation::getInstance($this->_phpExcel)->writeDebugLog = $saveDebugLog;
 	}
 
 	/**