title: ACS Error Page Compilation Error
body: <p>After upgrading from AEM6.0 to AEM6.1 the ACS Not Found pages are no longer working. If I visit the error page specifically (/content/PROJECT/en/errors/404.html), then it renders and everything is fine. I'm not sure what steps I should take to troubleshoot this problem.</p>
  
  <pre><code>28.10.2015 15:43:42.247 *ERROR* [10.43.32.4 [1446061422243] GET /notapage HTTP/1.1] org.apache.sling.engine.impl.DefaultErrorHandler  Error    handler failed:java.io.IOException
  java.io.IOException: Error handler failed: java.lang.Error
    at org.apache.sling.servlets.resolver.internal.SlingServletResolver.handleError(SlingServletResolver.java:771)
    at org.apache.sling.servlets.resolver.internal.SlingServletResolver.handleError(SlingServletResolver.java:442)
    at org.apache.sling.engine.impl.DefaultErrorHandler.handleError(DefaultErrorHandler.java:96)
    at org.apache.sling.engine.impl.SlingRequestProcessorImpl$1.render(SlingRequestProcessorImpl.java:345)
    at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:77)
    at org.apache.sling.i18n.impl.I18NFilter.doFilter(I18NFilter.java:129)
    at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:68)
    at org.apache.sling.rewriter.impl.RewriterFilter.doFilter(RewriterFilter.java:83)
    at org.apache.sling.engine.impl.filter.AbstractSlingFilterChain.doFilter(AbstractSlingFilterChain.java:68)
    at org.apache.sling.engine.impl.SlingRequestProcessorImpl.handleError(SlingRequestProcessorImpl.java:352)
    at org.apache.sling.engine.impl.SlingRequestProcessorImpl.doProcessRequest(SlingRequestProcessorImpl.java:167)
    at org.apache.sling.engine.impl.SlingMainServlet.service(SlingMainServlet.java:217)
    at org.apache.felix.http.base.internal.handler.ServletHandler.doHandle(ServletHandler.java:336)
    at org.apache.felix.http.base.internal.handler.ServletHandler.handle(ServletHandler.java:297)
    at org.apache.felix.http.base.internal.dispatch.ServletPipeline.handle(ServletPipeline.java:93)
    at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:50)
    at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
    at org.apache.sling.i18n.impl.I18NFilter.doFilter(I18NFilter.java:129)
    at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
    at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
    at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
    at com.adobe.granite.license.impl.LicenseCheckFilter.doFilter(LicenseCheckFilter.java:308)
    at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
    at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
    at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
    at org.apache.sling.security.impl.ReferrerFilter.doFilter(ReferrerFilter.java:290)
    at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
    at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
    at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
    at org.apache.felix.http.sslfilter.internal.SslFilter.doFilter(SslFilter.java:89)
    at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
    at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
    at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
    at org.apache.sling.featureflags.impl.FeatureManager.doFilter(FeatureManager.java:115)
    at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
    at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
    at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
    at org.apache.sling.engine.impl.log.RequestLoggerFilter.doFilter(RequestLoggerFilter.java:75)
    at org.apache.felix.http.base.internal.handler.FilterHandler.doHandle(FilterHandler.java:108)
    at org.apache.felix.http.base.internal.handler.FilterHandler.handle(FilterHandler.java:80)
    at org.apache.felix.http.base.internal.dispatch.InvocationFilterChain.doFilter(InvocationFilterChain.java:46)
    at org.apache.felix.http.base.internal.dispatch.HttpFilterChain.doFilter(HttpFilterChain.java:31)
    at org.apache.felix.http.base.internal.dispatch.FilterPipeline.dispatch(FilterPipeline.java:76)
    at org.apache.felix.http.base.internal.dispatch.Dispatcher.dispatch(Dispatcher.java:49)
    at org.apache.felix.http.base.internal.DispatcherServlet.service(DispatcherServlet.java:67)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:808)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:221)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:497)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
    at java.lang.Thread.run(Thread.java:745)
  Caused by: java.lang.Error: Unresolved compilation problems: 
    The type com.day.cq.wcm.api.Page cannot be resolved. It is indirectly referenced from required .class files
    The type com.day.cq.wcm.api.designer.Style cannot be resolved. It is indirectly referenced from required .class files
    The type com.day.cq.wcm.api.components.ComponentContext cannot be resolved. It is indirectly referenced from required .class files
    The type com.day.cq.wcm.api.components.Component cannot be resolved. It is indirectly referenced from required .class files
    Only a type can be imported. com.day.cq.wcm.api.Page resolves to a package
    Only a type can be imported. com.day.cq.wcm.api.NameConstants resolves to a package
    Only a type can be imported. com.day.cq.wcm.api.PageManager resolves to a package
    Only a type can be imported. com.day.cq.wcm.api.designer.Designer resolves to a package
    Only a type can be imported. com.day.cq.wcm.api.designer.Design resolves to a package
    Only a type can be imported. com.day.cq.wcm.api.designer.Style resolves to a package
    Only a type can be imported. com.day.cq.wcm.api.components.ComponentContext resolves to a package
    Only a type can be imported. com.day.cq.wcm.api.components.EditContext resolves to a package
    Only a type can be imported. com.day.cq.wcm.api.WCMMode resolves to a package
    com.day.cq.wcm.api.components.ComponentContext cannot be resolved to a type
    com.day.cq.wcm.api.components.EditContext cannot be resolved to a type
    com.day.cq.wcm.api.PageManager cannot be resolved to a type
    com.day.cq.wcm.api.Page cannot be resolved to a type
    com.day.cq.wcm.api.Page cannot be resolved to a type
    com.day.cq.wcm.api.components.Component cannot be resolved to a type
    com.day.cq.wcm.api.designer.Designer cannot be resolved to a type
    com.day.cq.wcm.api.designer.Design cannot be resolved to a type
    com.day.cq.wcm.api.designer.Design cannot be resolved to a type
    com.day.cq.wcm.api.designer.Style cannot be resolved to a type
    com.day.cq.wcm.api.components.ComponentContext cannot be resolved to a type
    com.day.cq.wcm.api.components.EditContext cannot be resolved to a type
    com.day.cq.wcm.api.PageManager cannot be resolved to a type
    com.day.cq.wcm.api.Page cannot be resolved to a type
    com.day.cq.wcm.api.Page cannot be resolved to a type
    com.day.cq.wcm.api.components.Component cannot be resolved to a type
    com.day.cq.wcm.api.designer.Designer cannot be resolved to a type
    com.day.cq.wcm.api.designer.Design cannot be resolved to a type
    com.day.cq.wcm.api.designer.Design cannot be resolved to a type
    com.day.cq.wcm.api.designer.Style cannot be resolved to a type
    WCMMode cannot be resolved
    WCMMode.DISABLED cannot be resolved to a type
  
    at org.apache.jsp.apps.sling.servlet.errorhandler._404_jsp.&lt;init&gt;(_404_jsp.java:1)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at java.lang.Class.newInstance(Class.java:379)
    at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.loadServlet(JspServletWrapper.java:165)
    at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.prepareServlet(JspServletWrapper.java:434)
    at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:486)
    at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:449)
    at org.apache.sling.scripting.jsp.JspScriptEngineFactory.callJsp(JspScriptEngineFactory.java:284)
    at org.apache.sling.scripting.jsp.JspScriptEngineFactory.access$100(JspScriptEngineFactory.java:102)
    at org.apache.sling.scripting.jsp.JspScriptEngineFactory$JspScriptEngine.eval(JspScriptEngineFactory.java:536)
    at org.apache.sling.scripting.core.impl.DefaultSlingScript.call(DefaultSlingScript.java:361)
    at org.apache.sling.scripting.core.impl.DefaultSlingScript.eval(DefaultSlingScript.java:171)
    at org.apache.sling.scripting.core.impl.DefaultSlingScript.service(DefaultSlingScript.java:463)
    at org.apache.sling.servlets.resolver.internal.SlingServletResolver.handleError(SlingServletResolver.java:762)
    ... 67 common frames omitted
  </code></pre>