diff --git a/src/main/java/org/gcube/portlets/user/td/expressionwidget/server/C_ExpressionParser.java b/src/main/java/org/gcube/portlets/user/td/expressionwidget/server/C_ExpressionParser.java
index 13527bf..c2c566f 100644
--- a/src/main/java/org/gcube/portlets/user/td/expressionwidget/server/C_ExpressionParser.java
+++ b/src/main/java/org/gcube/portlets/user/td/expressionwidget/server/C_ExpressionParser.java
@@ -623,8 +623,12 @@ public class C_ExpressionParser {
 		C_TextReplaceMatchingRegex textReplaceMatchingRegex = (C_TextReplaceMatchingRegex) exp;
 		TDText tdRegexp = new TDText(textReplaceMatchingRegex.getRegexp()
 				.getValue());
-		TDText tdReplacing = new TDText(textReplaceMatchingRegex.getReplacing()
-				.getValue());
+	
+		String replacement=textReplaceMatchingRegex.getReplacing().getValue();
+		if(replacement==null){
+			replacement="";
+		}
+		TDText tdReplacing = new TDText(replacement);
 
 		TextReplaceMatchingRegex textRepRegex = new TextReplaceMatchingRegex(
 				parse(textReplaceMatchingRegex.getToCheckText()), tdRegexp,