diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 7922c4425f4..fe8d42d75d9 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -85,9 +85,9 @@ jobs:
         # On top of this it's difficult to make it just run once on CI
         # without adding changes to more than a single file
         run: |
-          ERR=$(egrep 'Error |Warning ' -c make-check.log)
+          ERR=$(egrep 'Error \(|Warning \(' -c make-check.log)
           echo ERR=$ERR
-          test 5 -eq  "$ERR"
+          test 1 -eq  "$ERR"
 
       - name: Check all code in release mode
         # This should be removed when the preceding passes succeed
diff --git a/ocaml/libs/http-svr/server_io.ml b/ocaml/libs/http-svr/server_io.ml
index f1c204bb036..28fd584d1dc 100644
--- a/ocaml/libs/http-svr/server_io.ml
+++ b/ocaml/libs/http-svr/server_io.ml
@@ -37,33 +37,7 @@ exception PleaseClose
 
 let set_intersect a b = List.filter (fun x -> List.mem x b) a
 
-(** Establish a server; handler is either 'by_thread' or 'in_this_thread' *)
-type sock_or_addr =
-  | Server_sockaddr of Unix.sockaddr
-  | Server_fd of Unix.file_descr
-
-let establish_server ?(signal_fds = []) forker sockoraddr =
-  let sock =
-    match sockoraddr with
-    | Server_sockaddr sockaddr ->
-        let domain =
-          match sockaddr with
-          | ADDR_UNIX _ ->
-              debug "Establishing Unix domain server" ;
-              Unix.PF_UNIX
-          | ADDR_INET (_, _) ->
-              debug "Establishing inet domain server" ;
-              Unix.PF_INET
-        in
-        let sock = Unix.socket domain Unix.SOCK_STREAM 0 in
-        Unix.set_close_on_exec sock ;
-        Unix.setsockopt sock Unix.SO_REUSEADDR true ;
-        Unix.bind sock sockaddr ;
-        Unix.listen sock 5 ;
-        sock
-    | Server_fd fd ->
-        fd
-  in
+let establish_server ?(signal_fds = []) forker sock =
   while true do
     try
       let r, _, _ = Unix.select ([sock] @ signal_fds) [] [] (-1.) in
@@ -117,7 +91,7 @@ let server handler sock =
             try
               establish_server ~signal_fds:[status_out]
                 (handler_by_thread handler)
-                (Server_fd sock)
+                sock
             with PleaseClose -> debug "Server thread exiting"
           )
           ()
diff --git a/ocaml/libs/stunnel/stunnel.ml b/ocaml/libs/stunnel/stunnel.ml
index 0052e1d7974..062ebe1ba2b 100644
--- a/ocaml/libs/stunnel/stunnel.ml
+++ b/ocaml/libs/stunnel/stunnel.ml
@@ -92,15 +92,9 @@ module Unsafe = struct
 
   (* File descriptor operations to be performed after a fork.
    * These are all safe in the presence of threads *)
-  type fd_operation =
-    | Dup2 of Unix.file_descr * Unix.file_descr
-    | Close of Unix.file_descr
-
-  let do_fd_operation = function
-    | Dup2 (a, b) ->
-        Unix.dup2 a b
-    | Close a ->
-        Unix.close a
+  type fd_operation = Dup2 of Unix.file_descr * Unix.file_descr
+
+  let do_fd_operation = function Dup2 (a, b) -> Unix.dup2 a b
 end
 
 type pid =
diff --git a/ocaml/xenopsd/xc/device.ml b/ocaml/xenopsd/xc/device.ml
index 889939e66d9..a2e22c7ee2c 100644
--- a/ocaml/xenopsd/xc/device.ml
+++ b/ocaml/xenopsd/xc/device.ml
@@ -263,7 +263,7 @@ module Generic = struct
 
   let is_backend backend_type path =
     let affix = Printf.sprintf "backend/%s/" backend_type in
-    Astring.String.is_infix affix path
+    Astring.String.is_infix ~affix path
 
   let is_qdisk_or_9pfs x =
     let path = Hotplug.path_written_by_hotplug_scripts x in
@@ -708,7 +708,7 @@ module Vbd_Common = struct
             ("physical-device", physical_device)
           ; ("physical-device-path", physical_device_path)
           ]
-    | [vdi; tag; security_model; path] ->
+    | [_vdi; tag; security_model; path] ->
         List.iter
           (fun (k, v) -> Hashtbl.replace back_tbl k v)
           [("security_model", security_model); ("path", path)] ;