diff --git a/logback-classic/src/main/java/ch/qos/logback/classic/helpers/MDCInsertingServletFilter.java b/logback-classic/src/main/java/ch/qos/logback/classic/helpers/MDCInsertingServletFilter.java
index d4fba62160..3567d08d97 100644
--- a/logback-classic/src/main/java/ch/qos/logback/classic/helpers/MDCInsertingServletFilter.java
+++ b/logback-classic/src/main/java/ch/qos/logback/classic/helpers/MDCInsertingServletFilter.java
@@ -32,7 +32,9 @@
  * request into the MDC.
  * <p/>
  * <p/>
- * The values are removed after the request is processed.
+ * The values are removed after the all following
+ * filters/servlets have been processed. Note, however,
+ * the value is not available in an error handler servlet.
  *
  * @author Ceki G&uuml;lc&uuml;
  */
diff --git a/logback-examples/src/main/java/chapters/mdc/UserServletFilter.java b/logback-examples/src/main/java/chapters/mdc/UserServletFilter.java
index d7796715aa..cfb85b1d31 100644
--- a/logback-examples/src/main/java/chapters/mdc/UserServletFilter.java
+++ b/logback-examples/src/main/java/chapters/mdc/UserServletFilter.java
@@ -27,11 +27,12 @@
 import org.slf4j.MDC;
 
 /**
- * A simple servlet filter that puts the username
- * found either in the Principal.
+ * A simple servlet filter that stores the username
+ * found in the Principal in the MDC.
  * 
- * <p> The value is removed from the MDC once the request has been
- * fully processed.
+ * <p> The value is removed from the MDC once all following
+ * filters/servlets have been fully processed. Note, however,
+ * the value is not available in an error handler servlet.
  *
  * @author S&eacute;bastien Pennec
  */
@@ -74,7 +75,7 @@ public void init(FilterConfig arg0) throws ServletException {
      * @return true id the user can be successfully registered
      */
     private boolean registerUsername(String username) {
-        if (username != null && username.trim().length() > 0) {
+        if (username != null && !username.trim().isEmpty()) {
             MDC.put(USER_KEY, username);
             return true;
         }