PEP 3123: Provide forward compatibility with Python 3.0, while keeping
backwards compatibility. Add Py_Refcnt, Py_Type, Py_Size, and
PyVarObject_HEAD_INIT.
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 840570e..2f2b35e 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -675,8 +675,8 @@
 /* This is only useful when running memory debuggers such as
  * Purify or Valgrind.  Uncomment to use.
  *
-#define Py_USING_MEMORY_DEBUGGER
  */
+#define Py_USING_MEMORY_DEBUGGER
 
 #ifdef Py_USING_MEMORY_DEBUGGER