diff --git a/file_hasher.h b/file_hasher.h
index e26ef96..48e075e 100644
--- a/file_hasher.h
+++ b/file_hasher.h
@@ -41,6 +41,7 @@
   }
   virtual const char *salt(void) { return salt_; }
 
+  virtual ~FileHasher() {};
   static int WriteCallback(void *file,
                            sector_t start,
                            u8 *dst,