diff --git a/packages/caqti-lwt/caqti-lwt.0.11.0/opam b/packages/caqti-lwt/caqti-lwt.0.11.0/opam
index 1c23a1c7154..dfdb6c73e86 100644
--- a/packages/caqti-lwt/caqti-lwt.0.11.0/opam
+++ b/packages/caqti-lwt/caqti-lwt.0.11.0/opam
@@ -16,7 +16,7 @@ depends: [
   "caqti-driver-sqlite3" {with-test & = "0.11.0"}
   "jbuilder" {>= "1.0+beta19"}
   "logs"
-  "lwt" {>= "3.2.0"}
+  "lwt" {>= "3.2.0" & < "6~"}
 ]
 conflicts: [
   "dune" {>= "1.10.0"}
diff --git a/packages/caqti-lwt/caqti-lwt.1.0.0/opam b/packages/caqti-lwt/caqti-lwt.1.0.0/opam
index 2ae8d5fff7a..eabffb626b7 100644
--- a/packages/caqti-lwt/caqti-lwt.1.0.0/opam
+++ b/packages/caqti-lwt/caqti-lwt.1.0.0/opam
@@ -12,7 +12,7 @@ depends: [
   "caqti-driver-sqlite3" {with-test & >= "1.0.0" & < "2.0.0~"}
   "dune"
   "logs"
-  "lwt" {>= "3.2.0"}
+  "lwt" {>= "3.2.0" & < "6~"}
 ]
 build: [
   ["dune" "build" "-p" name "-j" jobs]
diff --git a/packages/caqti-lwt/caqti-lwt.1.2.0/opam b/packages/caqti-lwt/caqti-lwt.1.2.0/opam
index a55a1e67e82..ed7e4c53f1d 100644
--- a/packages/caqti-lwt/caqti-lwt.1.2.0/opam
+++ b/packages/caqti-lwt/caqti-lwt.1.2.0/opam
@@ -12,7 +12,7 @@ depends: [
   "caqti-driver-sqlite3" {with-test & >= "1.0.0" & < "2.0.0~"}
   "dune" {>= "1.11"}
   "logs"
-  "lwt" {>= "3.2.0"}
+  "lwt" {>= "3.2.0" & < "6~"}
 ]
 build: [
   ["dune" "build" "-p" name "-j" jobs]
diff --git a/packages/caqti-lwt/caqti-lwt.1.3.0/opam b/packages/caqti-lwt/caqti-lwt.1.3.0/opam
index 06a29b40c69..84e3e2c5795 100644
--- a/packages/caqti-lwt/caqti-lwt.1.3.0/opam
+++ b/packages/caqti-lwt/caqti-lwt.1.3.0/opam
@@ -12,7 +12,7 @@ depends: [
   "caqti-driver-sqlite3" {with-test & >= "1.0.0" & < "2.0.0~"}
   "dune" {>= "1.11"}
   "logs"
-  "lwt" {>= "3.2.0"}
+  "lwt" {>= "3.2.0" & < "6~"}
 ]
 build: [
   ["dune" "build" "-p" name "-j" jobs]
diff --git a/packages/caqti-lwt/caqti-lwt.1.6.0/opam b/packages/caqti-lwt/caqti-lwt.1.6.0/opam
index 6b7a52d9988..cb4b4e280e0 100644
--- a/packages/caqti-lwt/caqti-lwt.1.6.0/opam
+++ b/packages/caqti-lwt/caqti-lwt.1.6.0/opam
@@ -12,7 +12,7 @@ depends: [
   "caqti-driver-sqlite3" {with-test & >= "1.0.0" & < "2.0.0~"}
   "dune" {>= "1.11"}
   "logs"
-  "lwt" {>= "3.2.0"}
+  "lwt" {>= "3.2.0" & < "6~"}
 ]
 build: [
   ["dune" "build" "-p" name "-j" jobs]
diff --git a/packages/caqti-lwt/caqti-lwt.1.7.0/opam b/packages/caqti-lwt/caqti-lwt.1.7.0/opam
index 38d50701876..16d06cccda8 100644
--- a/packages/caqti-lwt/caqti-lwt.1.7.0/opam
+++ b/packages/caqti-lwt/caqti-lwt.1.7.0/opam
@@ -14,7 +14,7 @@ depends: [
   "cmdliner" {with-test & < "1.1.0"}
   "dune" {>= "2.0"}
   "logs"
-  "lwt" {>= "3.2.0"}
+  "lwt" {>= "3.2.0" & < "6~"}
   "ocaml"
   "odoc" {with-doc}
 ]
diff --git a/packages/caqti-lwt/caqti-lwt.1.8.0/opam b/packages/caqti-lwt/caqti-lwt.1.8.0/opam
index 6f51cec2af7..66b32169470 100644
--- a/packages/caqti-lwt/caqti-lwt.1.8.0/opam
+++ b/packages/caqti-lwt/caqti-lwt.1.8.0/opam
@@ -14,7 +14,7 @@ depends: [
   "cmdliner" {with-test & >= "1.1.0"}
   "dune" {>= "2.0"}
   "logs"
-  "lwt" {>= "3.2.0"}
+  "lwt" {>= "3.2.0" & < "6~"}
   "ocaml"
   "odoc" {with-doc}
 ]
diff --git a/packages/caqti-lwt/caqti-lwt.1.9.0/opam b/packages/caqti-lwt/caqti-lwt.1.9.0/opam
index 583173a4ea5..8a17fa9bb1d 100644
--- a/packages/caqti-lwt/caqti-lwt.1.9.0/opam
+++ b/packages/caqti-lwt/caqti-lwt.1.9.0/opam
@@ -14,7 +14,7 @@ depends: [
   "cmdliner" {with-test & >= "1.1.0"}
   "dune" {>= "2.0"}
   "logs"
-  "lwt" {>= "3.2.0"}
+  "lwt" {>= "3.2.0" & < "6~"}
   "ocaml"
   "odoc" {with-doc}
 ]
diff --git a/packages/caqti-lwt/caqti-lwt.2.0.1/opam b/packages/caqti-lwt/caqti-lwt.2.0.1/opam
index 39af306d5d3..f54d09460a1 100644
--- a/packages/caqti-lwt/caqti-lwt.2.0.1/opam
+++ b/packages/caqti-lwt/caqti-lwt.2.0.1/opam
@@ -15,7 +15,7 @@ depends: [
   "dune" {>= "2.5"}
   "logs"
   "mtime" {>= "2.0.0"}
-  "lwt" {>= "5.3.0"}
+  "lwt" {>= "5.3.0" & < "6~"}
   "ocaml"
   "odoc" {with-doc}
 ]
diff --git a/packages/caqti-lwt/caqti-lwt.2.1.1/opam b/packages/caqti-lwt/caqti-lwt.2.1.1/opam
index 05efee3083b..7be2d21e39e 100644
--- a/packages/caqti-lwt/caqti-lwt.2.1.1/opam
+++ b/packages/caqti-lwt/caqti-lwt.2.1.1/opam
@@ -12,7 +12,7 @@ depends: [
   "ipaddr"
   "logs"
   "mtime" {>= "2.0.0"}
-  "lwt" {>= "5.3.0"}
+  "lwt" {>= "5.3.0" & < "6~"}
   "ocaml"
   "alcotest" {with-test & >= "1.5.0"}
   "alcotest-lwt" {with-test & >= "1.5.0"}
diff --git a/packages/caqti-lwt/caqti-lwt.2.2.4/opam b/packages/caqti-lwt/caqti-lwt.2.2.4/opam
index 9bbe40346f8..cdf862ed846 100644
--- a/packages/caqti-lwt/caqti-lwt.2.2.4/opam
+++ b/packages/caqti-lwt/caqti-lwt.2.2.4/opam
@@ -12,7 +12,7 @@ depends: [
   "ipaddr"
   "logs"
   "mtime" {>= "2.0.0"}
-  "lwt" {>= "5.3.0"}
+  "lwt" {>= "5.3.0" & < "6~"}
   "ocaml"
   "alcotest" {with-test & >= "1.5.0"}
   "alcotest-lwt" {with-test & >= "1.5.0"}
diff --git a/packages/conf-glib-2/conf-glib-2.1/opam b/packages/conf-glib-2/conf-glib-2.1/opam
index 4289f5cfef4..a722202c7ee 100644
--- a/packages/conf-glib-2/conf-glib-2.1/opam
+++ b/packages/conf-glib-2/conf-glib-2.1/opam
@@ -4,7 +4,11 @@ maintainer: "Anton Bachin <antonbachin@yahoo.com>"
 homepage: "https://wiki.gnome.org/Projects/GLib"
 bug-reports: "https://github.com/ocaml/opam-repository/issues"
 license: "LGPL-2.0-only"
-build: [["pkg-config" "glib-2.0"]]
+build: [
+  "pkgconf" {os = "win32" & os-distribution != "cygwinports"}
+  "pkg-config" {os != "win32" | os-distribution != "cygwin"}
+  "glib-2.0"
+]
 depexts: [
   ["libglib2.0-dev"] {os-family = "debian"}
   ["libglib2.0-dev"] {os-family = "ubuntu"}
diff --git a/packages/curl_lwt/curl_lwt.0.10.0/opam b/packages/curl_lwt/curl_lwt.0.10.0/opam
index d3caf98f9bf..d9b42793a04 100644
--- a/packages/curl_lwt/curl_lwt.0.10.0/opam
+++ b/packages/curl_lwt/curl_lwt.0.10.0/opam
@@ -14,7 +14,7 @@ depends: [
   "ocaml" {>= "4.11"}
   "base-unix"
   "curl" {= version}
-  "lwt"
+  "lwt" {< "6~"}
   "lwt_ppx" {with-dev-setup}
   "odoc" {with-doc}
 ]
diff --git a/packages/lambda-term/lambda-term.1.13/opam b/packages/lambda-term/lambda-term.1.13/opam
index 97878f34f31..5e7aa6a919a 100644
--- a/packages/lambda-term/lambda-term.1.13/opam
+++ b/packages/lambda-term/lambda-term.1.13/opam
@@ -12,7 +12,7 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.02.3"}
-  "lwt" {>= "4.0.0"}
+  "lwt" {>= "4.0.0" & < "6~"}
   "lwt_log"
   "react"
   "zed" {>= "1.2" & < "2.0"}
diff --git a/packages/lambda-term/lambda-term.2.0.1/opam b/packages/lambda-term/lambda-term.2.0.1/opam
index 7ec43688b33..9c72c1cab85 100644
--- a/packages/lambda-term/lambda-term.2.0.1/opam
+++ b/packages/lambda-term/lambda-term.2.0.1/opam
@@ -12,7 +12,7 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.02.3"}
-  "lwt"   {>= "4.0.0"}
+  "lwt" {>= "4.0.0" & < "6~"}
   "lwt_log"
   "react"
   "zed"   {>= "2.0" & < "3.0"}
diff --git a/packages/lambda-term/lambda-term.2.0.2/opam b/packages/lambda-term/lambda-term.2.0.2/opam
index 29a5a6ebb3c..9d68e0d0f58 100644
--- a/packages/lambda-term/lambda-term.2.0.2/opam
+++ b/packages/lambda-term/lambda-term.2.0.2/opam
@@ -11,7 +11,7 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.02.3"}
-  "lwt"   {>= "4.0.0"}
+  "lwt" {>= "4.0.0" & < "6~"}
   "lwt_log"
   "react"
   "zed"   {>= "2.0.3" & < "3.0"}
diff --git a/packages/lambda-term/lambda-term.2.0.3/opam b/packages/lambda-term/lambda-term.2.0.3/opam
index 2b3602bb78c..826187b26f6 100644
--- a/packages/lambda-term/lambda-term.2.0.3/opam
+++ b/packages/lambda-term/lambda-term.2.0.3/opam
@@ -11,7 +11,7 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.02.3"}
-  "lwt"   {>= "4.0.0"}
+  "lwt" {>= "4.0.0" & < "6~"}
   "lwt_log"
   "react"
   "zed"   {>= "2.0.3" & < "3.0"}
diff --git a/packages/lambda-term/lambda-term.2.0/opam b/packages/lambda-term/lambda-term.2.0/opam
index c0627e26b16..6160333bcee 100644
--- a/packages/lambda-term/lambda-term.2.0/opam
+++ b/packages/lambda-term/lambda-term.2.0/opam
@@ -12,7 +12,7 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.02.3"}
-  "lwt"   {>= "4.0.0"}
+  "lwt" {>= "4.0.0" & < "6~"}
   "lwt_log"
   "react"
   "zed"   {>= "2.0" & < "3.0"}
diff --git a/packages/lambda-term/lambda-term.3.0.0/opam b/packages/lambda-term/lambda-term.3.0.0/opam
index 43ee8ceafe8..30f64469655 100644
--- a/packages/lambda-term/lambda-term.3.0.0/opam
+++ b/packages/lambda-term/lambda-term.3.0.0/opam
@@ -11,7 +11,7 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.02.3"}
-  "lwt"   {>= "4.2.0"}
+  "lwt" {>= "4.2.0" & < "6~"}
   "lwt_log"
   "react"
   "zed" {>= "3.0.0" & < "3.2.0"}
diff --git a/packages/lambda-term/lambda-term.3.0.1/opam b/packages/lambda-term/lambda-term.3.0.1/opam
index 219e73d3b1a..b680783e5b6 100644
--- a/packages/lambda-term/lambda-term.3.0.1/opam
+++ b/packages/lambda-term/lambda-term.3.0.1/opam
@@ -11,7 +11,7 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.02.3"}
-  "lwt"   {>= "4.2.0"}
+  "lwt" {>= "4.2.0" & < "6~"}
   "lwt_log"
   "react"
   "zed" {>= "3.0.0" & < "3.2.0"}
diff --git a/packages/lambda-term/lambda-term.3.1.0/opam b/packages/lambda-term/lambda-term.3.1.0/opam
index a20559a542a..d54ea702c9a 100644
--- a/packages/lambda-term/lambda-term.3.1.0/opam
+++ b/packages/lambda-term/lambda-term.3.1.0/opam
@@ -11,7 +11,7 @@ build: [
 ]
 depends: [
   "ocaml" {>= "4.02.3"}
-  "lwt"   {>= "4.2.0"}
+  "lwt" {>= "4.2.0" & < "6~"}
   "lwt_log"
   "react"
   "zed" {>= "3.1.0" & < "3.2.0"}
diff --git a/packages/lambda-term/lambda-term.3.2.0/opam b/packages/lambda-term/lambda-term.3.2.0/opam
index b109ee019a4..c3ebc57addb 100644
--- a/packages/lambda-term/lambda-term.3.2.0/opam
+++ b/packages/lambda-term/lambda-term.3.2.0/opam
@@ -15,7 +15,7 @@ homepage: "https://github.com/ocaml-community/lambda-term"
 bug-reports: "https://github.com/ocaml-community/lambda-term/issues"
 depends: [
   "ocaml" {>= "4.08.0"}
-  "lwt" {>= "4.0.0"}
+  "lwt" {>= "4.0.0" & < "6~"}
   "lwt_log"
   "react"
   "zed" {>= "3.1.0" & < "3.2.0"}
diff --git a/packages/lambda-term/lambda-term.3.3.0/opam b/packages/lambda-term/lambda-term.3.3.0/opam
index 72e23c12715..a8256e0cf61 100644
--- a/packages/lambda-term/lambda-term.3.3.0/opam
+++ b/packages/lambda-term/lambda-term.3.3.0/opam
@@ -17,7 +17,7 @@ bug-reports: "https://github.com/ocaml-community/lambda-term/issues"
 depends: [
   "dune" {>= "3.0"}
   "ocaml" {>= "4.08.0" & < "5.0"}
-  "lwt" {>= "4.2.0"}
+  "lwt" {>= "4.2.0" & < "6~"}
   "lwt_log"
   "lwt_react"
   "mew_vi" {>= "0.5.0" & < "0.6.0"}
diff --git a/packages/lambda-term/lambda-term.3.3.1/opam b/packages/lambda-term/lambda-term.3.3.1/opam
index 3a814ebae36..97f1ca64ec9 100644
--- a/packages/lambda-term/lambda-term.3.3.1/opam
+++ b/packages/lambda-term/lambda-term.3.3.1/opam
@@ -17,7 +17,7 @@ depends: [
   "dune" {>= "3.0"}
   "ocaml" {>= "4.08.0"}
   "logs"
-  "lwt" {>= "4.2.0"}
+  "lwt" {>= "4.2.0" & < "6~"}
   "lwt_react"
   "mew_vi" {>= "0.5.0" & < "0.6.0"}
   "react"
diff --git a/packages/lambda-term/lambda-term.3.3.2/opam b/packages/lambda-term/lambda-term.3.3.2/opam
index 66fc69572db..c48b4aef0ac 100644
--- a/packages/lambda-term/lambda-term.3.3.2/opam
+++ b/packages/lambda-term/lambda-term.3.3.2/opam
@@ -17,7 +17,7 @@ depends: [
   "dune" {>= "3.0"}
   "ocaml" {>= "4.08.0"}
   "logs"
-  "lwt" {>= "4.2.0"}
+  "lwt" {>= "4.2.0" & < "6~"}
   "lwt_react"
   "mew_vi" {>= "0.5.0" & < "0.6.0"}
   "react"
diff --git a/packages/lwt/lwt.6.0.0~alpha01/opam b/packages/lwt/lwt.6.0.0~alpha01/opam
new file mode 100644
index 00000000000..66c48105d7b
--- /dev/null
+++ b/packages/lwt/lwt.6.0.0~alpha01/opam
@@ -0,0 +1,69 @@
+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+synopsis: "Promises and event-driven I/O"
+description: """
+A promise is a value that may become determined in the future.
+
+Lwt provides typed, composable promises. Promises that are resolved by I/O are
+resolved by Lwt in parallel.
+
+Meanwhile, OCaml code, including code creating and waiting on promises, runs in
+a single thread by default. This reduces the need for locks or other
+synchronization primitives. Code can be run in parallel on an opt-in basis.
+"""
+maintainer: [
+  "Raphaël Proust <code@bnwr.net>" "Anton Bachin <antonbachin@yahoo.com>"
+]
+authors: ["Jérôme Vouillon" "Jérémie Dimino"]
+license: "MIT"
+homepage: "https://github.com/ocsigen/lwt"
+doc: "https://ocsigen.org/lwt"
+bug-reports: "https://github.com/ocsigen/lwt/issues"
+depends: [
+  "dune" {>= "2.7"}
+  "ocaml" {>= "4.14"}
+  "domain_shims"
+  "cppo" {build & >= "1.1.0"}
+  "ocamlfind" {dev & >= "1.7.3-1"}
+  "odoc" {with-doc & >= "2.3.0"}
+  "bisect_ppx" {with-test}
+  "dune-configurator"
+  "ocplib-endian"
+]
+depopts: ["base-threads" "base-unix" "conf-libev"]
+dev-repo: "git+https://github.com/ocsigen/lwt.git"
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "exec"
+    "-p"
+    name
+    "src/unix/config/discover.exe"
+    "--"
+    "--save"
+    "--use-libev" "%{conf-libev:installed}%"
+  ]
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+]
+x-maintenance-intent:[ "(latest)" ]
+available: opam-version >= "2.1.0"
+flags: avoid-version
+url {
+  src:
+    "https://github.com/ocsigen/lwt/archive/refs/tags/6.0.0-alpha01.tar.gz"
+  checksum: [
+    "md5=33a91da42f38f86555d633bf847fdb19"
+    "sha512=1c6c5784d0cdbdd265ef71d3b64dd16f5d5ec68d98227154d6301d15fde7d16e273d83819028747762fb4ba3c3ae8833ce308e581b6be8447f8775982c9f6be9"
+  ]
+}
diff --git a/packages/lwt_direct/lwt_direct.6.0.0~alpha01/opam b/packages/lwt_direct/lwt_direct.6.0.0~alpha01/opam
new file mode 100644
index 00000000000..3a11edda20f
--- /dev/null
+++ b/packages/lwt_direct/lwt_direct.6.0.0~alpha01/opam
@@ -0,0 +1,44 @@
+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+synopsis: "Direct-style control-flow and `await` for Lwt"
+maintainer: [
+  "Raphaël Proust <code@bnwr.net>" "Anton Bachin <antonbachin@yahoo.com>"
+]
+authors: ["Simon Cruanes"]
+license: "MIT"
+homepage: "https://github.com/ocsigen/lwt"
+doc: "https://ocsigen.org/lwt"
+bug-reports: "https://github.com/ocsigen/lwt/issues"
+depends: [
+  "dune" {>= "2.7"}
+  "ocaml" {>= "5.0"}
+  "base-unix"
+  "lwt" {= version}
+  "bisect_ppx" {with-test}
+  "odoc" {with-doc}
+]
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+]
+dev-repo: "git+https://github.com/ocsigen/lwt.git"
+available: opam-version >= "2.1.0"
+flags: avoid-version
+url {
+  src:
+    "https://github.com/ocsigen/lwt/archive/refs/tags/6.0.0-alpha01.tar.gz"
+  checksum: [
+    "md5=33a91da42f38f86555d633bf847fdb19"
+    "sha512=1c6c5784d0cdbdd265ef71d3b64dd16f5d5ec68d98227154d6301d15fde7d16e273d83819028747762fb4ba3c3ae8833ce308e581b6be8447f8775982c9f6be9"
+  ]
+}
diff --git a/packages/lwt_glib/lwt_glib.1.0.1/opam b/packages/lwt_glib/lwt_glib.1.0.1/opam
index 96256680200..033c4398415 100644
--- a/packages/lwt_glib/lwt_glib.1.0.1/opam
+++ b/packages/lwt_glib/lwt_glib.1.0.1/opam
@@ -23,7 +23,7 @@ remove: [
 depends: [
   "ocaml" {< "5.0.0"}
   "ocamlfind" {build}
-  "lwt" {>= "3.0.0"}
+  "lwt" {>= "3.0.0" & < "6~"}
   "base-unix"
   "conf-pkg-config" {build}
   "conf-glib-2" {build}
diff --git a/packages/lwt_glib/lwt_glib.1.1.0/opam b/packages/lwt_glib/lwt_glib.1.1.0/opam
index e8a0f6ed534..ab1b566a6ee 100644
--- a/packages/lwt_glib/lwt_glib.1.1.0/opam
+++ b/packages/lwt_glib/lwt_glib.1.1.0/opam
@@ -23,7 +23,7 @@ depends: [
   "conf-glib-2" {build}
   "conf-pkg-config" {build}
   "jbuilder" {>= "1.0+beta10"}
-  "lwt" {>= "3.0.0"}
+  "lwt" {>= "3.0.0" & < "6~"}
 ]
 synopsis: "GLib integration for Lwt"
 url {
diff --git a/packages/lwt_glib/lwt_glib.1.1.1/opam b/packages/lwt_glib/lwt_glib.1.1.1/opam
index ef424efa8a6..efdae414be7 100644
--- a/packages/lwt_glib/lwt_glib.1.1.1/opam
+++ b/packages/lwt_glib/lwt_glib.1.1.1/opam
@@ -16,7 +16,7 @@ depends: [
   "conf-glib-2" {build}
   "conf-pkg-config" {build}
   "dune"
-  "lwt" {>= "3.0.0"}
+  "lwt" {>= "3.0.0" & < "6~"}
   "ocaml"
 ]
 
diff --git a/packages/lwt_log/lwt_log.1.1.0/opam b/packages/lwt_log/lwt_log.1.1.0/opam
index 960671815dd..10051de5097 100644
--- a/packages/lwt_log/lwt_log.1.1.0/opam
+++ b/packages/lwt_log/lwt_log.1.1.0/opam
@@ -13,7 +13,7 @@ dev-repo: "git+https://github.com/aantron/lwt_log.git"
 depends: [
   "ocaml" {< "5.0"}
   "jbuilder" {>= "1.0+beta10"}
-  "lwt" {>= "4.0.0"}
+  "lwt" {>= "4.0.0" & < "6~"}
 ]
 build: [
   ["jbuilder" "build" "-p" name "-j" jobs]
diff --git a/packages/lwt_log/lwt_log.1.1.1/opam b/packages/lwt_log/lwt_log.1.1.1/opam
index 97174cdef92..7583bee8946 100644
--- a/packages/lwt_log/lwt_log.1.1.1/opam
+++ b/packages/lwt_log/lwt_log.1.1.1/opam
@@ -17,7 +17,7 @@ dev-repo: "git+https://github.com/ocsigen/lwt_log.git"
 depends: [
   "ocaml" {< "5.0"}
   "dune" {>= "1.0"}
-  "lwt" {>= "4.0.0"}
+  "lwt" {>= "4.0.0" & < "6~"}
 ]
 
 build: [
diff --git a/packages/lwt_log/lwt_log.1.1.2/opam b/packages/lwt_log/lwt_log.1.1.2/opam
index f73df584b7a..c9769ef0c1b 100644
--- a/packages/lwt_log/lwt_log.1.1.2/opam
+++ b/packages/lwt_log/lwt_log.1.1.2/opam
@@ -16,7 +16,7 @@ dev-repo: "git+https://github.com/ocsigen/lwt_log.git"
 depends: [
   "dune" {>= "1.0"}
   "lwt" {>= "4.0.0"}
-  "ocaml" {>= "4.03"}
+  "ocaml" {>= "4.03" & < "6~"}
 ]
 
 build: [
diff --git a/packages/lwt_ppx/lwt_ppx.5.8.1/opam b/packages/lwt_ppx/lwt_ppx.5.8.1/opam
index c79da3975b7..cdfc440bef4 100644
--- a/packages/lwt_ppx/lwt_ppx.5.8.1/opam
+++ b/packages/lwt_ppx/lwt_ppx.5.8.1/opam
@@ -14,7 +14,7 @@ depends: [
   "dune" {>= "2.7"}
   "ocaml" {>= "4.08"}
   "ppxlib" {>= "0.16.0" & < "0.36"}
-  "lwt" {>= "5.7.0"}
+  "lwt" {>= "5.7.0" & < "6~"}
   "odoc" {with-doc}
 ]
 build: [
diff --git a/packages/mwt/mwt.0.1.0/opam b/packages/mwt/mwt.0.1.0/opam
index 451cb713bb6..7b402bbde09 100644
--- a/packages/mwt/mwt.0.1.0/opam
+++ b/packages/mwt/mwt.0.1.0/opam
@@ -15,7 +15,7 @@ depends: [
   "base-threads"
   "base-unix"
   "dune"
-  "lwt" {>= "2.7.0"}
+  "lwt" {>= "2.7.0" & < "6~"}
   "lwt_ppx"
 ]
 synopsis: "Mediumweight thread library for OCaml via Lwt"
diff --git a/packages/nocrypto/nocrypto.0.5.4-1/opam b/packages/nocrypto/nocrypto.0.5.4-1/opam
index 75864fa48ac..7c269842b11 100644
--- a/packages/nocrypto/nocrypto.0.5.4-1/opam
+++ b/packages/nocrypto/nocrypto.0.5.4-1/opam
@@ -26,7 +26,7 @@ depends: [
   "cstruct" {>= "3.0.0" & < "6.1.0"}
   "cstruct-lwt"
   "zarith"
-  "lwt"
+  "lwt" {< "6~"}
   "sexplib" {!= "v0.9.0"}
   ("mirage-no-xen" |
     ("mirage-xen" {>="2.2.0" & < "6.0.0"}
diff --git a/packages/nocrypto/nocrypto.0.5.4-2/opam b/packages/nocrypto/nocrypto.0.5.4-2/opam
index fe92eeb0b0d..fbd536813fb 100644
--- a/packages/nocrypto/nocrypto.0.5.4-2/opam
+++ b/packages/nocrypto/nocrypto.0.5.4-2/opam
@@ -27,7 +27,7 @@ depends: [
   "cstruct" {>= "3.0.0" & < "6.1.0"}
   "cstruct-lwt"
   "zarith"
-  "lwt"
+  "lwt" {< "6~"}
   "sexplib" {!= "v0.9.0"}
   ("mirage-no-xen" |
     ("mirage-xen" {>="2.2.0" & < "6.0.0"}
diff --git a/packages/ocurl/ocurl.0.7.6/opam b/packages/ocurl/ocurl.0.7.6/opam
index f740dd822a5..b087f28ae74 100644
--- a/packages/ocurl/ocurl.0.7.6/opam
+++ b/packages/ocurl/ocurl.0.7.6/opam
@@ -25,6 +25,7 @@ depends: [
 depopts: ["lwt"]
 conflicts: [
   "ocaml-option-bytecode-only"
+  "lwt" {> "6~"}
 ]
 patches: [ "examples.diff" ]
 synopsis: "Bindings to libcurl"
diff --git a/packages/ocurl/ocurl.0.7.7/opam b/packages/ocurl/ocurl.0.7.7/opam
index 8cba4bcb3e8..d213b57d8e0 100644
--- a/packages/ocurl/ocurl.0.7.7/opam
+++ b/packages/ocurl/ocurl.0.7.7/opam
@@ -25,6 +25,7 @@ depends: [
 depopts: ["lwt"]
 conflicts: [
   "ocaml-option-bytecode-only"
+  "lwt" {> "6~"}
 ]
 patches: ["fix_depend.diff"]
 synopsis: "Bindings to libcurl"
diff --git a/packages/ocurl/ocurl.0.7.8/opam b/packages/ocurl/ocurl.0.7.8/opam
index 23c4036975f..71295ba945d 100644
--- a/packages/ocurl/ocurl.0.7.8/opam
+++ b/packages/ocurl/ocurl.0.7.8/opam
@@ -25,6 +25,7 @@ depends: [
 depopts: ["lwt"]
 conflicts: [
   "ocaml-option-bytecode-only"
+  "lwt" {> "6~"}
 ]
 synopsis: "Bindings to libcurl"
 description: """
diff --git a/packages/ocurl/ocurl.0.7.9/opam b/packages/ocurl/ocurl.0.7.9/opam
index 5426d207c92..ea90a34314d 100644
--- a/packages/ocurl/ocurl.0.7.9/opam
+++ b/packages/ocurl/ocurl.0.7.9/opam
@@ -25,6 +25,7 @@ depends: [
 depopts: ["lwt"]
 conflicts: [
   "ocaml-option-bytecode-only"
+  "lwt" {> "6~"}
 ]
 synopsis: "Bindings to libcurl"
 description: """
diff --git a/packages/ocurl/ocurl.0.8.1/opam b/packages/ocurl/ocurl.0.8.1/opam
index 5c935c69008..e37e25e1121 100644
--- a/packages/ocurl/ocurl.0.8.1/opam
+++ b/packages/ocurl/ocurl.0.8.1/opam
@@ -26,6 +26,7 @@ depends: [
 depopts: ["lwt"]
 conflicts: [
   "lwt" {with-test & >= "5.0.0"}
+  "lwt" {> "6~"}
   "ocaml-option-bytecode-only"
 ]
 synopsis: "Bindings to libcurl"
diff --git a/packages/ocurl/ocurl.0.8.2/opam b/packages/ocurl/ocurl.0.8.2/opam
index 18088aa9a3e..a8622663a82 100644
--- a/packages/ocurl/ocurl.0.8.2/opam
+++ b/packages/ocurl/ocurl.0.8.2/opam
@@ -26,6 +26,7 @@ depends: [
 depopts: ["lwt"]
 conflicts: [
   "lwt" {with-test & >= "5.0.0"}
+  "lwt" {> "6~"}
   "ocaml-option-bytecode-only"
 ]
 synopsis: "Bindings to libcurl"
diff --git a/packages/ocurl/ocurl.0.9.0/opam b/packages/ocurl/ocurl.0.9.0/opam
index b23e5c690c5..c3d07a231e6 100644
--- a/packages/ocurl/ocurl.0.9.0/opam
+++ b/packages/ocurl/ocurl.0.9.0/opam
@@ -25,6 +25,7 @@ depends: [
 depopts: ["lwt" "lwt_ppx"]
 conflicts: [
   "lwt" {with-test & >= "5.0.0"}
+  "lwt" {> "6~"}
   "ocaml-option-bytecode-only"
 ]
 synopsis: "Bindings to libcurl"
diff --git a/packages/ocurl/ocurl.0.9.1/opam b/packages/ocurl/ocurl.0.9.1/opam
index f1a75880d26..d82948e2a65 100644
--- a/packages/ocurl/ocurl.0.9.1/opam
+++ b/packages/ocurl/ocurl.0.9.1/opam
@@ -24,6 +24,7 @@ depends: [
 ]
 conflicts: [
   "ocaml-option-bytecode-only"
+  "lwt" {> "6~"}
 ]
 depopts: ["lwt" "lwt_ppx"]
 synopsis: "Bindings to libcurl"
diff --git a/packages/ocurl/ocurl.0.9.2/opam b/packages/ocurl/ocurl.0.9.2/opam
index 08c09bb9c3d..afe5e1f633a 100644
--- a/packages/ocurl/ocurl.0.9.2/opam
+++ b/packages/ocurl/ocurl.0.9.2/opam
@@ -25,6 +25,7 @@ depends: [
 depopts: ["lwt" "lwt_ppx"]
 conflicts: [
   "ocaml-option-bytecode-only"
+  "lwt" {> "6~"}
 ]
 synopsis: "Bindings to libcurl"
 description: "libcurl is a client-side URL transfer library, supporting HTTP and a multitude of other network protocols (FTP/SMTP/RTSP/etc). This library wrap easy synchronous API (Curl), synchronous parallel and generic asynchronous API (Curl.Multi), and provides an Lwt-enabled asynchronous interface (Curl_lwt)."
diff --git a/packages/tezt/tezt.3.1.0/opam b/packages/tezt/tezt.3.1.0/opam
index 389840732f7..ddf5e43237f 100644
--- a/packages/tezt/tezt.3.1.0/opam
+++ b/packages/tezt/tezt.3.1.0/opam
@@ -9,7 +9,7 @@ depends: [
   "dune" { >= "3.0" }
   "ocaml" { >= "4.12" }
   "re" { >= "1.7.2" }
-  "lwt" { >= "5.6.0" }
+  "lwt" {>= "5.6.0" & < "6~"}
   "base-unix"
   "ezjsonm" { >= "1.1.0" }
   "conf-npm" { with-test }
diff --git a/packages/tezt/tezt.3.1.1/opam b/packages/tezt/tezt.3.1.1/opam
index a9e75054dd8..8af522c2ee7 100644
--- a/packages/tezt/tezt.3.1.1/opam
+++ b/packages/tezt/tezt.3.1.1/opam
@@ -9,7 +9,7 @@ depends: [
   "dune" { >= "3.0" }
   "ocaml" { >= "4.12" }
   "re" { >= "1.7.2" }
-  "lwt" { >= "5.6.0" }
+  "lwt" {>= "5.6.0" & < "6~"}
   "base-unix"
   "ezjsonm" { >= "1.1.0" }
   "conf-npm" { with-test }
diff --git a/packages/tezt/tezt.4.0.0/opam b/packages/tezt/tezt.4.0.0/opam
index 3eb0f45eadd..af52c9f929e 100644
--- a/packages/tezt/tezt.4.0.0/opam
+++ b/packages/tezt/tezt.4.0.0/opam
@@ -9,7 +9,7 @@ depends: [
   "dune" { >= "3.0" }
   "ocaml" { >= "4.12" }
   "re" { >= "1.7.2" }
-  "lwt" { >= "5.6.0" }
+  "lwt" {>= "5.6.0" & < "6~"}
   "base-unix"
   "ezjsonm" { >= "1.1.0" }
   "clap" { >= "0.3.0" }
diff --git a/packages/tezt/tezt.4.1.0/opam b/packages/tezt/tezt.4.1.0/opam
index f474351f218..a2f52f45432 100644
--- a/packages/tezt/tezt.4.1.0/opam
+++ b/packages/tezt/tezt.4.1.0/opam
@@ -9,7 +9,7 @@ depends: [
   "dune" { >= "3.0" }
   "ocaml" { >= "4.12" }
   "re" { >= "1.7.2" }
-  "lwt" { >= "5.6.0" }
+  "lwt" {>= "5.6.0" & < "6~"}
   "base-unix"
   "ezjsonm" { >= "1.1.0" }
   "clap" { >= "0.3.0" }
diff --git a/packages/tezt/tezt.4.2.0/opam b/packages/tezt/tezt.4.2.0/opam
index 6bbe8fdeb72..87c39f30697 100644
--- a/packages/tezt/tezt.4.2.0/opam
+++ b/packages/tezt/tezt.4.2.0/opam
@@ -9,7 +9,7 @@ depends: [
   "dune" { >= "3.0" }
   "ocaml" { >= "4.12" }
   "re" { >= "1.7.2" }
-  "lwt" { >= "5.6.0" }
+  "lwt" {>= "5.6.0" & < "6~"}
   "base-unix"
   "ezjsonm" { >= "1.1.0" }
   "clap" { >= "0.3.0" }