diff --git a/src/main/java/org/gcube/portlets/user/td/expressionwidget/server/ExpressionServiceImpl.java b/src/main/java/org/gcube/portlets/user/td/expressionwidget/server/ExpressionServiceImpl.java
index 8145e50..c06a4e1 100644
--- a/src/main/java/org/gcube/portlets/user/td/expressionwidget/server/ExpressionServiceImpl.java
+++ b/src/main/java/org/gcube/portlets/user/td/expressionwidget/server/ExpressionServiceImpl.java
@@ -29,6 +29,7 @@ import org.gcube.portlets.user.td.gwtservice.server.trservice.OperationsId;
 import org.gcube.portlets.user.td.gwtservice.server.trservice.TaskStateMap;
 import org.gcube.portlets.user.td.gwtservice.shared.Constants;
 import org.gcube.portlets.user.td.gwtservice.shared.exception.TDGWTServiceException;
+import org.gcube.portlets.user.td.gwtservice.shared.exception.TDGWTSessionExpiredException;
 import org.gcube.portlets.user.td.gwtservice.shared.tr.TabResource;
 import org.gcube.portlets.user.td.widgetcommonevent.shared.TRId;
 import org.slf4j.Logger;
@@ -100,7 +101,9 @@ public class ExpressionServiceImpl extends RemoteServiceServlet implements
 			logger.debug("Start Task on service: TaskId " + trTask.getId());
 			ExpressionSession.setColumnFilterTask(session, trTask);
 			return;
-		} catch (Exception e) {
+		} catch (TDGWTSessionExpiredException e){
+			throw new ExpressionServiceException(e.getLocalizedMessage());
+		} catch (Throwable e) {
 			e.printStackTrace();
 			throw new ExpressionServiceException(
 					"Error in Client Library Request: "
@@ -194,7 +197,9 @@ public class ExpressionServiceImpl extends RemoteServiceServlet implements
 
 			logger.info("ColumnFilterMonitor(): " + columnFilterMonitor);
 			return columnFilterMonitor;
-		} catch (Exception e) {
+		} catch (TDGWTSessionExpiredException e){
+			throw new ExpressionServiceException(e.getLocalizedMessage());
+		} catch (Throwable e) {
 			e.printStackTrace();
 			throw new ExpressionServiceException(
 					"Error applying column filter: " + e.getLocalizedMessage());
diff --git a/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/expression/ExpressionServiceException.java b/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/expression/ExpressionServiceException.java
index 776a2ae..4c8c86d 100644
--- a/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/expression/ExpressionServiceException.java
+++ b/src/main/java/org/gcube/portlets/user/td/expressionwidget/shared/expression/ExpressionServiceException.java
@@ -1,5 +1,6 @@
 package org.gcube.portlets.user.td.expressionwidget.shared.expression;
 
+
 public class ExpressionServiceException extends Exception {
 
 	private static final long serialVersionUID = -9066034060104406559L;