Index: Mapper.java
===================================================================
--- Mapper.java	(revision 1633619)
+++ Mapper.java	(working copy)
@@ -677,6 +677,10 @@
                     MappingData mappingData)
         throws Exception {
 
+    	if (defaultHostName == null) {
+    		return;
+    	}
+
         if (host.isNull()) {
             host.getCharChunk().append(defaultHostName);
         }
Index: MapperListener.java
===================================================================
--- MapperListener.java	(revision 1633619)
+++ MapperListener.java	(working copy)
@@ -257,35 +257,11 @@
 
         Engine engine = (Engine) service.getContainer();
         String defaultHost = engine.getDefaultHost();
-
-        boolean found = false;
-
-        if (defaultHost != null && defaultHost.length() >0) {
-            Container[] containers = engine.findChildren();
-
-            for (Container container : containers) {
-                Host host = (Host) container;
-                if (defaultHost.equalsIgnoreCase(host.getName())) {
-                    found = true;
-                    break;
-                }
-
-                String[] aliases = host.findAliases();
-                for (String alias : aliases) {
-                    if (defaultHost.equalsIgnoreCase(alias)) {
-                        found = true;
-                        break;
-                    }
-                }
-            }
-        }
-
-        if(found) {
-            mapper.setDefaultHostName(defaultHost);
-        } else {
-            log.warn(sm.getString("mapperListener.unknownDefaultHost",
-                    defaultHost, service));
-        }
+        
+        //Calling set default host directly because if we have 
+        //null as default host then Tomcat should stop instead 
+        //of just giving a warning
+        mapper.setDefaultHostName(defaultHost);
     }