Index: jython/src/org/python/core/PyFile.java
===================================================================
--- jython/src/org/python/core/PyFile.java	(revision 3670)
+++ jython/src/org/python/core/PyFile.java	(working copy)
@@ -1630,6 +1630,11 @@
         }
 
         public void run() {
+            if (closers == null) {
+                // It's been found that closers can be null at this
+                // point in some strange cases.
+                return;
+            }
             synchronized(closers) {
                 while(closers.size() > 0) {
                     try {