diff --git a/file_hasher.h b/file_hasher.h
index e26ef96..b086f96 100644
--- a/file_hasher.h
+++ b/file_hasher.h
@@ -25,6 +25,8 @@ class FileHasher {
                  destination_(NULL),
                  block_limit_(0),
                  alg_(NULL) { }
+  virtual ~FileHasher() { }
+
   // TODO(wad) add initialized_ variable to check.
   virtual bool Initialize(simple_file::File *source,
                           simple_file::File *destination,