diff -ur ../PyODE-snapshot-2010-03-22.orig/src/body.pyx ./src/body.pyx
--- ../PyODE-snapshot-2010-03-22.orig/src/body.pyx	2013-04-25 22:19:59.582137101 +1000
+++ ./src/body.pyx	2013-04-25 22:20:30.387025990 +1000
@@ -56,7 +56,7 @@
         self.userattribs = {}
 
     def __dealloc__(self):
-        if self.bid!=NULL:
+        if self.bid!=NULL and self.world:
             dBodyDestroy(self.bid)
 
     def __getattr__(self, name):
diff -ur ../PyODE-snapshot-2010-03-22.orig/src/joints.pyx ./src/joints.pyx
--- ../PyODE-snapshot-2010-03-22.orig/src/joints.pyx	2013-04-25 22:19:59.583137098 +1000
+++ ./src/joints.pyx	2013-04-25 22:20:38.613993565 +1000
@@ -121,7 +121,7 @@
 
     def __dealloc__(self):
         self.setFeedback(False)
-        if self.jid!=NULL:
+        if self.jid!=NULL and self.world:
             dJointDestroy(self.jid)
 
     def __getattr__(self, name):