1 files changed, 2 insertions, 1 deletions

diff --git a/cpp/nissy.h b/cpp/nissy.h
index 7ab466d..448704e 100644
--- a/cpp/nissy.h
+++ b/cpp/nissy.h
@@ -84,10 +84,11 @@ namespace nissy {
                 size_t size;
                 std::string id;
                 std::vector<std::byte> data;
+                bool data_checked;
 
                 error generate_data();
                 void read_data(std::ifstream&);
-                error check_data() const;
+                error check_data();
                 void unload_data();
                 solve_result solve(const cube&, nissflag, unsigned minmoves,
                     unsigned maxmoves, unsigned maxsols, int optimal,