diff --git a/persistent-data/space-maps/disk.cc b/persistent-data/space-maps/disk.cc
index c6c9c23..2f9f4ac 100644
--- a/persistent-data/space-maps/disk.cc
+++ b/persistent-data/space-maps/disk.cc
@@ -240,6 +240,8 @@ namespace {
 	public:
 		typedef boost::shared_ptr<index_store> ptr;
 
+		virtual ~index_store() {}
+
 		virtual void count_metadata(block_counter &bc) const = 0;
 		virtual void resize(block_address nr_indexes) = 0;
 		virtual index_entry find_ie(block_address b) const = 0;