diff --git a/src/main/java/org/gcube/portlets/user/statisticalalgorithmsimporter/server/generator/AlgorithmGenerator.java b/src/main/java/org/gcube/portlets/user/statisticalalgorithmsimporter/server/generator/AlgorithmGenerator.java
index ee76a44..0916659 100644
--- a/src/main/java/org/gcube/portlets/user/statisticalalgorithmsimporter/server/generator/AlgorithmGenerator.java
+++ b/src/main/java/org/gcube/portlets/user/statisticalalgorithmsimporter/server/generator/AlgorithmGenerator.java
@@ -258,16 +258,19 @@ public class AlgorithmGenerator {
 		}
 
 		for (InputOutputVariables selVariable : project.getInputData().getListInputOutputVariables()) {
-			switch (selVariable.getIoType()) {
-			case INPUT:
-				code.add("		inputvariables.add(\"" + selVariable.getName() + "\");");
-				break;
-			case OUTPUT:
-				code.add("		outputvariables.add(\"" + selVariable.getName() + "\");");
-				break;
-			default:
-				break;
+			if (selVariable != null && selVariable.getDataType() != null
+					&& selVariable.getDataType().compareTo(DataType.SYSTEM) != 0) {
+				switch (selVariable.getIoType()) {
+				case INPUT:
+					code.add("		inputvariables.add(\"" + selVariable.getName() + "\");");
+					break;
+				case OUTPUT:
+					code.add("		outputvariables.add(\"" + selVariable.getName() + "\");");
+					break;
+				default:
+					break;
 
+				}
 			}
 		}