diff --git a/.merlin b/.merlin
index 728816da..933075fd 100644
--- a/.merlin
+++ b/.merlin
@@ -15,4 +15,4 @@ PKG benchmark
 PKG threads
 PKG threads.posix
 PKG lwt
-FLG -w +K,+Y,+X
+FLG -w +a -w -4 -w -44
diff --git a/_tags b/_tags
index 5a3bb15a..37a53b13 100644
--- a/_tags
+++ b/_tags
@@ -160,4 +160,4 @@
 <tests/*.ml{,i}>: thread
 <threads/*.ml{,i}>: thread
 <sequence>: -traverse
-<{string,core}/**/*.ml>: warn_A, warn(-4)
+<{string,core}/**/*.ml>: warn_A, warn(-4), warn(-44)
diff --git a/core/CCList.ml b/core/CCList.ml
index 03713d62..64cd4b9e 100644
--- a/core/CCList.ml
+++ b/core/CCList.ml
@@ -552,7 +552,7 @@ module type MONAD = sig
 end
 
 module Traverse(M : MONAD) = struct
-  open! M
+  open M
 
   let map_m f l =
     let rec aux f acc l = match l with