Index: include/xapian/base.h
===================================================================
--- include/xapian/base.h	(revision 9809)
+++ include/xapian/base.h	(working copy)
@@ -123,7 +123,10 @@
     T *old_dest = dest;
     dest = dest_;
     if (dest) ++dest->ref_count;
-    if (old_dest && --old_dest->ref_count == 0) delete old_dest;
+    if (old_dest && --old_dest->ref_count == 0) {
+	delete old_dest;
+	memset(old_dest, 0, sizeof(T));
+    }
 }
 
 template <class T>
@@ -136,6 +139,7 @@
 	T * condemned = dest;
 	dest = 0;
 	delete condemned;
+	memset(condemned, 0, sizeof(T));
     }
 }