diff --git a/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFColor.java b/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFColor.java
index fc5304a0aa..b2cb8747a1 100644
--- a/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFColor.java
+++ b/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFColor.java
@@ -25,7 +25,7 @@ import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTColor;
  * Represents a color in SpreadsheetML
  */
 public class XSSFColor extends ExtendedColor {
-    private CTColor ctColor;
+    private final CTColor ctColor;
 
     /**
      * Create an instance of XSSFColor from the supplied XML bean