diff --git a/master_changes.md b/master_changes.md
index 257f80afc58..4043210b8b2 100644
--- a/master_changes.md
+++ b/master_changes.md
@@ -53,6 +53,7 @@ users)
   * Fix extra-files handling when linting packages from repositories, see #5068 [#5639 @rjbou]
 
 ## Repository
+  * Fix `OPAMCURL` and `OPAMFETCH` handling [#5607 @rjbou - fix #5597]
 
 ## Lock
 
diff --git a/src/repository/opamRepositoryConfig.ml b/src/repository/opamRepositoryConfig.ml
index 373177e9f20..306f3be8237 100644
--- a/src/repository/opamRepositoryConfig.ml
+++ b/src/repository/opamRepositoryConfig.ml
@@ -122,13 +122,19 @@ let initk k =
               (CString cmd, None), `Default
           in
           let c = cmd :: List.map (fun a -> OpamTypes.CString a, None) a in
-          Some (lazy (c, kind))
+          Some (c, kind)
         | [] ->
           None
       )
-    >>+ fun () ->
-    E.curl () >>| (fun s ->
-        lazy ([CString s, None], `Curl))
+    |> (fun fetch ->
+        match E.curl (), fetch with
+        | None, fetch -> OpamStd.Option.map Lazy.from_val fetch
+        | Some cmd, Some (((CIdent "curl"| CString "curl"), filter)::args, _) ->
+          Some (lazy ((CString cmd, filter)::args, `Curl))
+        | Some cmd, None ->
+          Some (lazy ([CString cmd, None], `Curl))
+        | Some _, _ -> (* ignored *)
+          OpamStd.Option.map Lazy.from_val fetch)
   in
   let validation_hook =
     E.validationhook () >>| fun s ->
diff --git a/tests/reftests/download.test b/tests/reftests/download.test
index 1155197fd34..fd7c9de4e21 100644
--- a/tests/reftests/download.test
+++ b/tests/reftests/download.test
@@ -88,9 +88,9 @@ The following actions will be performed:
 <><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
 Processing  1/1: [foo.1: http]
 + curl "--another-args" "3"
-[ERROR] Failed to get sources of foo.1: Curl failed
+[ERROR] Failed to get sources of foo.1: curl error code ***The curl is a lie*** [args: --another-args 3]
 
-OpamSolution.Fetch_fail("https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz (Curl failed: \"curl --another-args 3\" exited with code 2)")
+OpamSolution.Fetch_fail("https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz (curl: code ***The curl is a lie*** [args: --another-args 3] while downloading https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz)")
 
 
 <><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
@@ -100,7 +100,7 @@ OpamSolution.Fetch_fail("https://github.com/UnixJunkie/get_line/archive/v1.0.0.t
 Clearing cache of downloaded files
 ### :I:e: FETCH curl & local curl
 ### OPAMFETCH=curl OPAMCURL=$BASEDIR/bin/curl
-### opam install foo --download-only | grep -v "^+-" | sed-cmd curl | sed-cmd tar | "${OPAMVERSION}" -> "current"
+### opam install foo --download-only | grep -v "^+-" | sed-cmd curl | "${OPAMVERSION}" -> "current"
 The following actions will be performed:
 === install 1 package
   - install foo 1
@@ -108,9 +108,14 @@ The following actions will be performed:
 <><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
 Processing  1/1: [foo.1: http]
 + curl "--write-out" "%{http_code}\n" "--retry" "3" "--retry-delay" "2" "--user-agent" "opam/current" "-L" "-o" "${BASEDIR}/OPAM/download/.opam-switch/sources/foo.1/v1.0.0.tar.gz.part" "--" "https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz"
-Processing  1/1:
-+ tar "xfz" "${OPAMTMP}/v1.0.0.tar.gz" "-C" "${OPAMTMP}"
-Done.
+[ERROR] Failed to get sources of foo.1: curl error code ***The curl is a lie*** [args: --write-out %{http_code}\n --retry 3 --retry-delay 2 --user-agent opam/current -L -o ${BASEDIR}/OPAM/download/.opam-switch/sources/foo.1/v1.0.0.tar.gz.part -- https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz]
+
+OpamSolution.Fetch_fail("https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz (curl: code ***The curl is a lie*** [args: --write-out %{http_code}\n --retry 3 --retry-delay 2 --user-agent opam/current -L -o ${BASEDIR}/OPAM/download/.opam-switch/sources/foo.1/v1.0.0.tar.gz.part -- https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz] while downloading https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz)")
+
+
+<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+'${OPAM} install foo --download-only' failed.
+# Return code 40 #
 ### opam clean -c
 Clearing cache of downloaded files
 ### :I:f: FETCH curl with args & local curl
@@ -123,9 +128,9 @@ The following actions will be performed:
 <><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
 Processing  1/1: [foo.1: http]
 + curl "--another-args" "3"
-[ERROR] Failed to get sources of foo.1: Curl failed
+[ERROR] Failed to get sources of foo.1: curl error code ***The curl is a lie*** [args: --another-args 3]
 
-OpamSolution.Fetch_fail("https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz (Curl failed: \"curl --another-args 3\" exited with code 2)")
+OpamSolution.Fetch_fail("https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz (curl: code ***The curl is a lie*** [args: --another-args 3] while downloading https://github.com/UnixJunkie/get_line/archive/v1.0.0.tar.gz)")
 
 
 <><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>