Removed line is back again.

diff --git a/helm/software/matita/nlibrary/nat/nat.ma b/helm/software/matita/nlibrary/nat/nat.ma
index eed1efd1c83a907ed4c247e65d1a2ab9608fcd2a..e9d32973bdb02a10caba88490cd84603209feee4 100644 (file)
--- a/helm/software/matita/nlibrary/nat/nat.ma
+++ b/helm/software/matita/nlibrary/nat/nat.ma
@@ -14,6 +14,7 @@
 
 include "hints_declaration.ma".
 include "logic/equality.ma".
+include "sets/setoids.ma".
 
 ninductive nat: Type[0] ≝
    O: nat