diff -Naur vmd-1.8.6/src/py_atomsel.C vmd-1.8.6.new/src/py_atomsel.C
--- vmd-1.8.6/src/py_atomsel.C	2007-04-08 01:04:03.000000000 -0400
+++ vmd-1.8.6.new/src/py_atomsel.C	2007-09-20 09:27:33.000000000 -0400
@@ -25,6 +25,11 @@
 #include "py_commands.h"
 #include "BondSearch.h"
 
+
+#if PY_VERSION_HEX < ((2<<24)|(5<<16))
+typedef int Py_ssize_t;
+#endif
+
 typedef struct {
   PyObject_HEAD
   AtomSel *atomSel;
@@ -915,7 +920,7 @@
  * Support for mapping protocol 
  */
 
-static int
+static Py_ssize_t
 atomselection_length( PyAtomSelObject *a ) {
   return a->atomSel->selected;
 }