diff --git a/src/fib/moonpool_fib.ml b/src/fib/moonpool_fib.ml
index ec89c075..0a3b7360 100644
--- a/src/fib/moonpool_fib.ml
+++ b/src/fib/moonpool_fib.ml
@@ -5,8 +5,15 @@
     @since 0.6. *)
 
 module Fiber = Fiber
+[@@deprecated "use picos structured concurrency or something else"]
+
 module Fls = Fls
 module Handle = Handle
+
 module Main = Main
+[@@deprecated "use picos structured concurrency or something else"]
+
+[@@@ocaml.alert "-deprecated"]
+
 include Fiber
 include Main