diff --git a/Classes/PHPExcel.php b/Classes/PHPExcel.php
index 29d0aa0f..e01581a2 100644
--- a/Classes/PHPExcel.php
+++ b/Classes/PHPExcel.php
@@ -527,6 +527,11 @@ class PHPExcel
                 ++$this->_activeSheetIndex;
             }
         }
+
+        if ($pSheet->getParent() === null) {
+            $pSheet->rebindParent($this);
+        }
+
         return $pSheet;
     }
 
diff --git a/Classes/PHPExcel/Worksheet.php b/Classes/PHPExcel/Worksheet.php
index 753e9c2a..b61f76e6 100644
--- a/Classes/PHPExcel/Worksheet.php
+++ b/Classes/PHPExcel/Worksheet.php
@@ -794,14 +794,16 @@ class PHPExcel_Worksheet implements PHPExcel_IComparable
      * @return PHPExcel_Worksheet
      */
 	public function rebindParent(PHPExcel $parent) {
-        $namedRanges = $this->_parent->getNamedRanges();
-        foreach ($namedRanges as $namedRange) {
-            $parent->addNamedRange($namedRange);
-        }
+        if ($this->_parent !== null) {
+            $namedRanges = $this->_parent->getNamedRanges();
+            foreach ($namedRanges as $namedRange) {
+                $parent->addNamedRange($namedRange);
+            }
 
-        $this->_parent->removeSheetByIndex(
-            $this->_parent->getIndex($this)
-        );
+            $this->_parent->removeSheetByIndex(
+                $this->_parent->getIndex($this)
+            );
+        }
         $this->_parent = $parent;
 
         return $this;
diff --git a/changelog.txt b/changelog.txt
index 96f97c6d..1d1222b9 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -46,6 +46,7 @@ Fixed in develop branch for release v1.8.0:
 - Bugfix:   (Roy Shahbazian)  Work Item GH-299  - Fixed typo in Chart/Layout set/getYMode()
 - Bugfix:   (EliuFlorez)      Work item GH-279  - Fatal error: Call to a member function cellExists() line: 3327 in calculation.php if referenced worksheet doesn't exist
 - Bugfix:   (MBaker)          Work Item GH-290  - AdvancedValueBinder "Division by zero"-error
+- Bugfix:   (MBaker)          Work Item CP20604 - Adding Sheet to Workbook Bug
 - Feature:  (amerov)                            - Implementation of the Excel HLOOKUP() function
 - Feature:  (MBaker)                            - Added "Quote Prefix" to style settings (Excel2007 Reader and Writer only)
 - Feature:  (MBaker)                            - Added Horizontal FILL alignment for Excel5 and Excel2007 Readers/Writers, and Horizontal DISTRIBUTED alignment for Excel2007 Reader/Writer