diff --git a/src/fib/coop_lock.ml b/src/core/coop_lock.ml
similarity index 98%
rename from src/fib/coop_lock.ml
rename to src/core/coop_lock.ml
index eb42f792..469d4ae4 100644
--- a/src/fib/coop_lock.ml
+++ b/src/core/coop_lock.ml
@@ -27,7 +27,7 @@ let rec lock_ (self : 'a t) : 'a =
   let old = A.get self.st in
   if old.locked then (
     (* suspend and add myself to the [waiters] queue *)
-    Moonpool.Private.Suspend_.suspend
+    Suspend_.suspend
       {
         handle =
           (fun ~run:_ ~resume k ->
diff --git a/src/fib/coop_lock.mli b/src/core/coop_lock.mli
similarity index 71%
rename from src/fib/coop_lock.mli
rename to src/core/coop_lock.mli
index 894878e5..0d5f451c 100644
--- a/src/fib/coop_lock.mli
+++ b/src/core/coop_lock.mli
@@ -5,8 +5,12 @@ type 'a t
 val create : 'a -> 'a t
 (** New lock *)
 
+[@@@ifge 5.0]
+
 val with_lock : 'a t -> ('a -> 'b) -> 'b
-(** [with_lock lock f]  calls [f] with the lock's content *)
+(** [with_lock lock f]  calls [f] with the lock's content. *)
 
 val with_lock_update : 'a t -> ('a -> 'a * 'b) -> 'b
 val with_try_lock : 'a t -> ('a option -> 'b) -> 'b
+
+[@@@endif]
diff --git a/src/core/moonpool.ml b/src/core/moonpool.ml
index cafac26c..4c02ad44 100644
--- a/src/core/moonpool.ml
+++ b/src/core/moonpool.ml
@@ -23,6 +23,7 @@ module Blocking_queue = Bb_queue
 module Background_thread = Background_thread
 module Bounded_queue = Bounded_queue
 module Chan = Chan
+module Coop_lock = Coop_lock
 module Exn_bt = Exn_bt
 module Fifo_pool = Fifo_pool
 module Fut = Fut
diff --git a/src/core/moonpool.mli b/src/core/moonpool.mli
index c0d495c9..fe20b3d1 100644
--- a/src/core/moonpool.mli
+++ b/src/core/moonpool.mli
@@ -75,6 +75,7 @@ val await : 'a Fut.t -> 'a
 [@@@endif]
 
 module Lock = Lock
+module Coop_lock = Coop_lock
 module Fut = Fut
 module Chan = Chan
 module Task_local_storage = Task_local_storage
diff --git a/src/fib/moonpool_fib.ml b/src/fib/moonpool_fib.ml
index 9359303f..ec89c075 100644
--- a/src/fib/moonpool_fib.ml
+++ b/src/fib/moonpool_fib.ml
@@ -8,6 +8,5 @@ module Fiber = Fiber
 module Fls = Fls
 module Handle = Handle
 module Main = Main
-module Coop_lock = Coop_lock
 include Fiber
 include Main