Index: java/org/apache/catalina/loader/WebappClassLoader.java
===================================================================
--- java/org/apache/catalina/loader/WebappClassLoader.java	(revision 1199160)
+++ java/org/apache/catalina/loader/WebappClassLoader.java	(working copy)
@@ -188,7 +188,7 @@
      * earlier versions.
      */
     protected static final String[] triggers = {
-        "javax.servlet.Servlet"                     // Servlet API
+        "javax.servlet.Servlet", "javax.el.Expression"       // Servlet API
     };
 
 
@@ -3280,6 +3280,10 @@
             // Web apps should never package any other Servlet or JSP classes
             return false;
         }
+        if (name.startsWith("javax.el")) {
+            // Must never load javax.el.* classes
+            return false;
+        }
 
         // Assume everything else is OK
         return true;