diff --git a/packages/MlFront_Cli/MlFront_Cli.0.4.0~prerel7/opam b/packages/MlFront_Cli/MlFront_Cli.0.4.0~prerel7/opam
index edbe17b16e3..b06de0ff654 100644
--- a/packages/MlFront_Cli/MlFront_Cli.0.4.0~prerel7/opam
+++ b/packages/MlFront_Cli/MlFront_Cli.0.4.0~prerel7/opam
@@ -23,9 +23,8 @@ depends: [
   "tezt" {with-test & >= "4.1.0"}
   "odoc" {with-doc}
 ]
-conflicts: [
-  "base-effects"
-]
+conflicts: "ocaml-variants" {= "5.1.1+effect-syntax"}
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
 build: [
   [
     "sh"
@@ -49,4 +48,4 @@ url {
     "md5=eaaecad4dfce5ad6849444bfa1e0cc44"
     "sha512=9cf976ec567c41101249a4cc1f57dedac14597f664d44ab8d25d1507812357ab038a6d47fe7e4450d25114e7f9edcedbcf78c1e24267858d8b7b0c12fb15c22b"
   ]
-}
\ No newline at end of file
+}
diff --git a/packages/coq-core/coq-core.8.17.0/opam b/packages/coq-core/coq-core.8.17.0/opam
index 68dcb712392..f3a42414c6e 100644
--- a/packages/coq-core/coq-core.8.17.0/opam
+++ b/packages/coq-core/coq-core.8.17.0/opam
@@ -34,8 +34,9 @@ depends: [
 conflicts: [
   "coq"   { < "8.17" }
   "ocaml-option-bytecode-only"
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 ]
+build-env: OCAMLPARAM = "_,w=-46,warn-error=-a,keywords=5.2"
 build: [
   [ "./configure"
     "-prefix" prefix
diff --git a/packages/coq-core/coq-core.8.17.1/opam b/packages/coq-core/coq-core.8.17.1/opam
index 18ee90399d5..e55d4fe1eb2 100644
--- a/packages/coq-core/coq-core.8.17.1/opam
+++ b/packages/coq-core/coq-core.8.17.1/opam
@@ -33,8 +33,9 @@ depends: [
 ]
 conflicts: [
   "coq"   { < "8.17" }
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 ]
+build-env: OCAMLPARAM = "_,w=-46,warn-error=-a,keywords=5.2"
 build: [
   [ "./configure"
     "-prefix" prefix
diff --git a/packages/coq-core/coq-core.8.18.0/opam b/packages/coq-core/coq-core.8.18.0/opam
index 0f6a394f413..bf01a68c090 100644
--- a/packages/coq-core/coq-core.8.18.0/opam
+++ b/packages/coq-core/coq-core.8.18.0/opam
@@ -34,8 +34,9 @@ depends: [
 ]
 conflicts: [
   "coq"   { < "8.17" }
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 ]
+build-env: OCAMLPARAM = "_,w=-46,warn-error=-a,keywords=5.2"
 build: [
   # Requires dune 2.8 due to https://github.com/ocaml/dune/issues/3219
   # ["dune" "subst"] {pinned}
diff --git a/packages/coq-core/coq-core.8.19.0/opam b/packages/coq-core/coq-core.8.19.0/opam
index eba0dcb4d0e..327c7665ea8 100644
--- a/packages/coq-core/coq-core.8.19.0/opam
+++ b/packages/coq-core/coq-core.8.19.0/opam
@@ -34,10 +34,11 @@ depends: [
 ]
 conflicts: [
   "coq"   { < "8.17" }
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 ]
 depopts: ["coq-native"]
 dev-repo: "git+https://github.com/coq/coq.git"
+build-env: OCAMLPARAM = "_,w=-46,warn-error=-a,keywords=5.2"
 build: [
   ["dune" "subst"] {dev}
   [ "./configure"
diff --git a/packages/coq-core/coq-core.8.19.1/opam b/packages/coq-core/coq-core.8.19.1/opam
index e4db743b83e..fe01aa82be1 100644
--- a/packages/coq-core/coq-core.8.19.1/opam
+++ b/packages/coq-core/coq-core.8.19.1/opam
@@ -34,10 +34,11 @@ depends: [
 ]
 conflicts: [
   "coq"   { < "8.17" }
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 ]
 depopts: ["coq-native"]
 dev-repo: "git+https://github.com/coq/coq.git"
+build-env: OCAMLPARAM = "_,w=-46,warn-error=-a,keywords=5.2"
 build: [
   ["dune" "subst"] {dev}
   [ "./configure"
diff --git a/packages/mock/mock.1.0.0/opam b/packages/mock/mock.1.0.0/opam
index 072039baaaf..7bf532cec3c 100644
--- a/packages/mock/mock.1.0.0/opam
+++ b/packages/mock/mock.1.0.0/opam
@@ -6,6 +6,7 @@ bug-reports: "https://github.com/cryptosense/ocaml-mock/issues"
 license: "BSD-2-Clause"
 dev-repo: "git+https://github.com/cryptosense/ocaml-mock.git"
 doc: "https://cryptosense.github.io/ocaml-mock/doc"
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
 build: [
   [ "dune" "build" "-p" name "-j" jobs ]
 ]
@@ -13,9 +14,7 @@ depends: [
   "dune"
   "ocaml" {>= "4.07.0"}
 ]
-conflicts: [
-  "base-effects"
-]
+conflicts: "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 synopsis: "Configurable functions to test impure code"
 description: """
 This package provides "mocks", fake functions that can be configured to return
diff --git a/packages/mopsa/mopsa.1.0/opam b/packages/mopsa/mopsa.1.0/opam
index 0aaea20a978..ee6f7860247 100644
--- a/packages/mopsa/mopsa.1.0/opam
+++ b/packages/mopsa/mopsa.1.0/opam
@@ -37,11 +37,10 @@ depends: [
   "odoc" {with-doc}
 ]
 depopts: ["elina"]
-conflicts: [
-  "base-effects"
-]
+conflicts: "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 available:
   !(arch = "x86_32") & !(os-family = "windows") & opam-version >= "2.1.0"
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
 build: [
   ["./configure"] {os != "macos"}
   [
@@ -97,4 +96,4 @@ url {
     "md5=9f673f79708b44a7effb3b6bb3618d2c"
     "sha512=cb91cb428e43a22f1abbcb8219710d0c10a5b3756d0da392d4084b3b3a6157350776c596983e63def344f617d39964e91f244f60c07958695ee5c8c809a9f0f4"
   ]
-}
\ No newline at end of file
+}
diff --git a/packages/omake/omake.0.10.6/opam b/packages/omake/omake.0.10.6/opam
index b47726ffedc..4be77fdb18f 100644
--- a/packages/omake/omake.0.10.6/opam
+++ b/packages/omake/omake.0.10.6/opam
@@ -11,6 +11,8 @@ dev-repo: "git+https://github.com/ocaml-omake/omake.git"
 homepage: "http://projects.camlcity.org/projects/omake.html"
 bug-reports: "https://github.com/ocaml-omake/issues"
 
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
+
 build: [
   ["./configure" "-prefix" "%{prefix}%"]
   [make]
@@ -24,7 +26,7 @@ depends: [
   "ocaml" {>= "4.03.0"}
   "ocamlfind"
 ]
-conflicts: [ "base-effects" ]
+conflicts: "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 synopsis: "Build system designed for scalability and portability"
 
 url {
diff --git a/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.2/opam b/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.2/opam
index 41969286f61..fcbfaa62afc 100644
--- a/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.2/opam
+++ b/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.2/opam
@@ -14,9 +14,8 @@ depends: [
   "prbnmcn-cgrph" {= "0.0.2"}
   "odoc" {with-doc}
 ]
-conflicts: [
-  "base-effects"
-]
+conflicts: "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
 build: [
   ["dune" "subst"] {dev}
   [
diff --git a/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.3/opam b/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.3/opam
index d182d0252f4..2f9ef0fc4f0 100644
--- a/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.3/opam
+++ b/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.3/opam
@@ -17,9 +17,8 @@ depends: [
   "prbnmcn-cgrph" {= "0.0.2"}
   "odoc" {with-doc}
 ]
-conflicts: [
-  "base-effects"
-]
+conflicts: "ocaml-variants" {= "5.1.1+effect-syntax"}
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
 build: [
   ["dune" "subst"] {dev}
   [
diff --git a/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.4/opam b/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.4/opam
index fe00e515354..2a9a619b887 100644
--- a/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.4/opam
+++ b/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.4/opam
@@ -18,9 +18,8 @@ depends: [
   "prbnmcn-cgrph" {= "0.0.2"}
   "odoc" {with-doc}
 ]
-conflicts: [
-  "base-effects"
-]
+conflicts: "ocaml-variants" {= "5.1.1+effect-syntax"}
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
 build: [
   ["dune" "subst"] {dev}
   [
diff --git a/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.5/opam b/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.5/opam
index 076ae526d43..8a73bfa49fb 100644
--- a/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.5/opam
+++ b/packages/prbnmcn-dagger/prbnmcn-dagger.0.0.5/opam
@@ -18,9 +18,8 @@ depends: [
   "prbnmcn-cgrph" {= "0.0.2"}
   "odoc" {with-doc}
 ]
-conflicts: [
-  "base-effects"
-]
+conflicts: "ocaml-variants" {= "5.1.1+effect-syntax"}
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
 build: [
   ["dune" "subst"] {dev}
   [
diff --git a/packages/why3/why3.1.6.0/opam b/packages/why3/why3.1.6.0/opam
index 9ec3cdffdf3..e9a546dc162 100644
--- a/packages/why3/why3.1.6.0/opam
+++ b/packages/why3/why3.1.6.0/opam
@@ -22,6 +22,8 @@ tags: [
   "interactive theorem prover"
 ]
 
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
+
 build: [
   ["./autogen.sh"] {dev} # when pinning, there might be no configure file
   ["./configure"
@@ -73,7 +75,7 @@ conflicts: [
   "why3-base"
   "ocamlgraph" {< "1.8.2"}
   "mlmpfr" {< "4.0.0"}
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
   "ocaml-option-bytecode-only"
 ]
 
diff --git a/packages/why3/why3.1.7.0/opam b/packages/why3/why3.1.7.0/opam
index 4e60957ea05..9b806f7b736 100644
--- a/packages/why3/why3.1.7.0/opam
+++ b/packages/why3/why3.1.7.0/opam
@@ -22,6 +22,8 @@ tags: [
   "interactive theorem prover"
 ]
 
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
+
 build: [
   ["./autogen.sh"] {dev} # when pinning, there might be no configure file
   ["touch" "configure"]
@@ -74,7 +76,7 @@ conflicts: [
   "why3-base"
   "ocamlgraph" {< "1.8.2"}
   "mlmpfr" {< "4.0.0"}
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
   "ocaml-option-bytecode-only"
 ]
 
diff --git a/packages/why3/why3.1.7.1/opam b/packages/why3/why3.1.7.1/opam
index dfaaa62d355..7076fdc79c0 100644
--- a/packages/why3/why3.1.7.1/opam
+++ b/packages/why3/why3.1.7.1/opam
@@ -22,6 +22,8 @@ tags: [
   "interactive theorem prover"
 ]
 
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
+
 build: [
   ["./autogen.sh"] {dev} # when pinning, there might be no configure file
   ["touch" "configure"]
@@ -74,7 +76,7 @@ conflicts: [
   "why3-base"
   "ocamlgraph" {< "1.8.2"}
   "mlmpfr" {< "4.0.0"}
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
   "ocaml-option-bytecode-only"
 ]
 
diff --git a/packages/why3/why3.1.7.2/opam b/packages/why3/why3.1.7.2/opam
index e190b344cee..e737b221ecb 100644
--- a/packages/why3/why3.1.7.2/opam
+++ b/packages/why3/why3.1.7.2/opam
@@ -22,6 +22,8 @@ tags: [
   "interactive theorem prover"
 ]
 
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
+
 build: [
   ["./autogen.sh"] {dev} # when pinning, there might be no configure file
   ["touch" "configure"]
@@ -74,7 +76,7 @@ conflicts: [
   "why3-base"
   "ocamlgraph" {< "1.8.2"}
   "mlmpfr" {< "4.0.0"}
-  "base-effects"
+  "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 ]
 
 synopsis: "Why3 environment for deductive program verification"
diff --git a/packages/yocaml/yocaml.1.0.0/opam b/packages/yocaml/yocaml.1.0.0/opam
index 69a0acda9d1..eb8c570b2e5 100644
--- a/packages/yocaml/yocaml.1.0.0/opam
+++ b/packages/yocaml/yocaml.1.0.0/opam
@@ -3,6 +3,7 @@ synopsis: "YOCaml It is a static site generator, mostly written in OCaml"
 maintainer: "xhtmlboi@gmail.com"
 authors: [ "The XHTMLBoy <xhtmlboi@gmail.com>" ]
 
+build-env: OCAMLPARAM = "_,w=-46,keywords=5.2"
 build: [
   [ "dune" "subst" ] {dev}
   [ "dune" "build" "-p" name "-j" jobs ]
@@ -23,9 +24,7 @@ depends: [
   "alcotest" {with-test}
   "preface" { >= "1.0.0"}
 ]
-conflicts: [
-  "base-effects"
-]
+conflicts: "ocaml-variants" {= "4.12.0+domains+effects" | = "5.1.1+effect-syntax"}
 url {
   src:
     "https://github.com/xhtmlboi/yocaml/releases/download/v1.0.0/yocaml-1.0.0.tbz"