diff --git a/src/Tiny_httpd_server.ml b/src/Tiny_httpd_server.ml
index 26624d4b..227b92f6 100644
--- a/src/Tiny_httpd_server.ml
+++ b/src/Tiny_httpd_server.ml
@@ -973,6 +973,7 @@ module Unix_tcp_server_ = struct
           done;
 
           (* Wait for all threads to be done: this only works if all threads are done. *)
+          Unix.close sock;
           Sem_.acquire self.sem_max_connections.max self.sem_max_connections;
           ());
     }