1 files changed, 5 insertions, 0 deletions
diff --git a/lib/sail.c b/lib/sail.c
index c3fbe3b4..5530b462 100644
--- a/lib/sail.c
+++ b/lib/sail.c
@@ -323,6 +323,11 @@ void undefined_int(sail_int *rop, const int n)
   mpz_set_ui(*rop, (uint64_t) n);
 }
 
+void undefined_nat(sail_int *rop, const unit u)
+{
+  mpz_set_ui(*rop, 0);
+}
+
 inline
 void undefined_range(sail_int *rop, const sail_int l, const sail_int u)
 {