--- a/langtools/src/jdk.jshell/share/classes/jdk/jshell/TaskFactory.java	Fri Jan 06 14:16:45 2017 +0100
+++ b/langtools/src/jdk.jshell/share/classes/jdk/jshell/TaskFactory.java	Fri Jan 06 10:31:25 2017 -0800
@@ -161,6 +161,10 @@
         @Override
         public Diag diag(Diagnostic<? extends JavaFileObject> d) {
             SourceMemoryJavaFileObject smjfo = (SourceMemoryJavaFileObject) d.getSource();
+            if (smjfo == null) {
+                // Handle failure that doesn't preserve mapping
+                return new StringSourceHandler().diag(d);
+            }
             OuterWrap w = (OuterWrap) smjfo.getOrigin();
             return w.wrapDiag(d);
         }