diff --git a/Classes/PHPExcel/Style/NumberFormat.php b/Classes/PHPExcel/Style/NumberFormat.php
index 0d7d93d..e098f6f 100644
--- a/Classes/PHPExcel/Style/NumberFormat.php
+++ b/Classes/PHPExcel/Style/NumberFormat.php
@@ -120,6 +120,7 @@ class PHPExcel_Style_NumberFormat extends PHPExcel_Style_Supervisor implements P
 
 		if ($isConditional) {
 			$this->_formatCode = NULL;
+			$this->_builtInFormatCode = FALSE;
 		}
 	}
 
diff --git a/changelog.txt b/changelog.txt
index 0ae0d63..1af29b2 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -45,6 +45,7 @@ Planned for v1.8.1
 - Feature:  (CQD)             Work Item GH-389  - Additional Mac CJK codepage definitions
 - Feature:  (bolovincev)      Work Item GH-269  - Update Worksheet.php getStyleByColumnAndRow() to allow a range of cells rather than just a single cell
 - Feature:  (MBaker)                            - New methods added for testing cell status within merge groups
+- Bugfix:   (wiseloren)       Work Item CP21454 - "No Impact" conditional formatting fix for NumberFormat
 
 
 2014-03-02 (v1.8.0):