diff --git a/jetty-webapp/src/main/java/org/eclipse/jetty/webapp/WebAppClassLoader.java b/jetty-webapp/src/main/java/org/eclipse/jetty/webapp/WebAppClassLoader.java
index b2b455a6a14..30582fe9841 100644
--- a/jetty-webapp/src/main/java/org/eclipse/jetty/webapp/WebAppClassLoader.java
+++ b/jetty-webapp/src/main/java/org/eclipse/jetty/webapp/WebAppClassLoader.java
@@ -511,7 +511,8 @@ public class WebAppClassLoader extends URLClassLoader
 
             if (c == null && ex!=null)
             {
-                LOG.debug("!loadedClass({}) from={} tried_parent={}",name,this,tried_parent);
+                if (LOG.isDebugEnabled())
+                    LOG.debug("!loadedClass({}) from={} tried_parent={}",name,this,tried_parent);
                 throw ex;
             }