$ diff master HEAD

...
diff --git a/src/mapgen.h b/src/mapgen.h
index 5d1e3bd..d090dd2 100644
--- a/src/mapgen.h
+++ b/src/mapgen.h
@@ -143,6 +143,7 @@ class Ore {
                np      = NULL;
                noise   = NULL;
        }
+       virtual ~Ore() {}
        
        virtual ~Ore();
        
...