diff --git a/packages/js_of_ocaml-compiler/js_of_ocaml-compiler.4.0.0+flambda2/opam b/packages/js_of_ocaml-compiler/js_of_ocaml-compiler.4.0.0+flambda2/opam
index af2500a..12bd04d 100644
--- a/packages/js_of_ocaml-compiler/js_of_ocaml-compiler.4.0.0+flambda2/opam
+++ b/packages/js_of_ocaml-compiler/js_of_ocaml-compiler.4.0.0+flambda2/opam
@@ -11,7 +11,7 @@ doc: "https://ocsigen.org/js_of_ocaml/latest/manual/overview"
 bug-reports: "https://github.com/ocsigen/js_of_ocaml/issues"
 depends: [
   "dune" {>= "2.9"}
-  "ocaml-variants" {= "4.12.0+flambda1" | = "4.12.0+flambda2"| = "4.12.0+pr867+flambda2" }
+  "ocaml" {>= "4.04" & < "4.15"}
   "num" {with-test}
   "ppx_expect" {>= "v0.14.2" & with-test}
   "ppxlib" {>= "0.15.0"}
@@ -54,5 +54,5 @@ url {
   ]
 }
 x-commit-hash: "6fb1d008061b6c028c375b240882bb735d54a5bc"
-patches: ["js_of_ocaml.patch"]
+patches: ["js_of_ocaml.patch"]  { ?ocaml-variants:flambda-backend & ocaml-variants:flambda-backend }
 extra-files: [ ["js_of_ocaml.patch" "md5=94e0fbbd912a4bb87a5da4d74d5e7535"] ]
diff --git a/packages/js_of_ocaml/js_of_ocaml.4.0.0+flambda2/opam b/packages/js_of_ocaml/js_of_ocaml.4.0.0+flambda2/opam
index aaf4b13..21ef2f0 100644
--- a/packages/js_of_ocaml/js_of_ocaml.4.0.0+flambda2/opam
+++ b/packages/js_of_ocaml/js_of_ocaml.4.0.0+flambda2/opam
@@ -11,7 +11,7 @@ doc: "https://ocsigen.org/js_of_ocaml/latest/manual/overview"
 bug-reports: "https://github.com/ocsigen/js_of_ocaml/issues"
 depends: [
   "dune" {>= "2.9"}
-  "ocaml-variants" {= "4.12.0+flambda1" | = "4.12.0+flambda2"| = "4.12.0+pr867+flambda2" }
+  "ocaml" {>= "4.04"}
   "js_of_ocaml-compiler" {= version}
   "ppxlib" {>= "0.15"}
   "uchar"
@@ -45,5 +45,5 @@ url {
   ]
 }
 x-commit-hash: "6fb1d008061b6c028c375b240882bb735d54a5bc"
-patches: ["js_of_ocaml.patch"]
+patches: ["js_of_ocaml.patch"] { ?ocaml-variants:flambda-backend & ocaml-variants:flambda-backend }
 extra-files: [ ["js_of_ocaml.patch" "md5=94e0fbbd912a4bb87a5da4d74d5e7535"] ]
diff --git a/packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4/files/read_cma.patch b/packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4+flambda2/files/read_cma.patch
similarity index 100%
rename from packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4/files/read_cma.patch
rename to packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4+flambda2/files/read_cma.patch
diff --git a/packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4/opam b/packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4+flambda2/opam
similarity index 91%
rename from packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4/opam
rename to packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4+flambda2/opam
index 86aaaca..6cce016 100644
--- a/packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4/opam
+++ b/packages/ocaml-compiler-libs/ocaml-compiler-libs.v0.12.4+flambda2/opam
@@ -10,7 +10,7 @@ homepage: "https://github.com/janestreet/ocaml-compiler-libs"
 bug-reports: "https://github.com/janestreet/ocaml-compiler-libs/issues"
 depends: [
   "dune" {>= "2.8"}
-  "ocaml-variants" {= "4.12.0+flambda1" | = "4.12.0+flambda2"| = "4.12.0+pr867+flambda2" }
+  "ocaml" {>= "4.04.1"}
   "odoc" {with-doc}
 ]
 build: [
@@ -37,5 +37,5 @@ url {
   ]
 }
 x-commit-hash: "8cd12f18bb7171c2b67d661868c4271fae528d93"
-patches: ["read_cma.patch"]
+patches: ["read_cma.patch" { ?ocaml-variants:flambda-backend & ocaml-variants:flambda-backend } ]
 extra-files: [ ["read_cma.patch" "md5=2ebb9731c60412575f27f3af2293a2a9"] ]
diff --git a/packages/ocaml-variants/ocaml-variants.4.12.0+flambda1/files/ocaml-variants.config b/packages/ocaml-variants/ocaml-variants.4.12.0+flambda1/files/ocaml-variants.config
new file mode 100644
index 0000000..a9f12c6
--- /dev/null
+++ b/packages/ocaml-variants/ocaml-variants.4.12.0+flambda1/files/ocaml-variants.config
@@ -0,0 +1,2 @@
+opam-version: "2.0"
+variables { flambda-backend: true }
diff --git a/packages/ocaml-variants/ocaml-variants.4.12.0+flambda1/opam b/packages/ocaml-variants/ocaml-variants.4.12.0+flambda1/opam
index 0378e3d..9999eea 100644
--- a/packages/ocaml-variants/ocaml-variants.4.12.0+flambda1/opam
+++ b/packages/ocaml-variants/ocaml-variants.4.12.0+flambda1/opam
@@ -45,3 +45,4 @@ extra-source "alt-signal-stack.patch" {
   src: "https://github.com/ocaml/ocaml/commit/1eeb0e7fe595f5f9e1ea1edbdf785ff3b49feeeb.patch"
   checksum: "sha256=59de25b95409c1927c4b607fb4b1218ff7623fca45474448c8e114a42853e3ad"
 }
+extra-files: [ [ "ocaml-variants.config" "md5=2e903f01e0ca006dd7c6cc7e4ec4543f" ] ]
diff --git a/packages/ocaml-variants/ocaml-variants.4.12.0+flambda2/files/ocaml-variants.config b/packages/ocaml-variants/ocaml-variants.4.12.0+flambda2/files/ocaml-variants.config
new file mode 100644
index 0000000..a9f12c6
--- /dev/null
+++ b/packages/ocaml-variants/ocaml-variants.4.12.0+flambda2/files/ocaml-variants.config
@@ -0,0 +1,2 @@
+opam-version: "2.0"
+variables { flambda-backend: true }
diff --git a/packages/ocaml-variants/ocaml-variants.4.12.0+flambda2/opam b/packages/ocaml-variants/ocaml-variants.4.12.0+flambda2/opam
index e3deb87..8e7d606 100644
--- a/packages/ocaml-variants/ocaml-variants.4.12.0+flambda2/opam
+++ b/packages/ocaml-variants/ocaml-variants.4.12.0+flambda2/opam
@@ -45,3 +45,4 @@ extra-source "alt-signal-stack.patch" {
   src: "https://github.com/ocaml/ocaml/commit/1eeb0e7fe595f5f9e1ea1edbdf785ff3b49feeeb.patch"
   checksum: "sha256=59de25b95409c1927c4b607fb4b1218ff7623fca45474448c8e114a42853e3ad"
 }
+extra-files: [ [ "ocaml-variants.config" "md5=2e903f01e0ca006dd7c6cc7e4ec4543f" ] ]
diff --git a/packages/ocaml-variants/ocaml-variants.4.12.0+pr867+flambda2/files/ocaml-variants.config b/packages/ocaml-variants/ocaml-variants.4.12.0+pr867+flambda2/files/ocaml-variants.config
new file mode 100644
index 0000000..a9f12c6
--- /dev/null
+++ b/packages/ocaml-variants/ocaml-variants.4.12.0+pr867+flambda2/files/ocaml-variants.config
@@ -0,0 +1,2 @@
+opam-version: "2.0"
+variables { flambda-backend: true }
diff --git a/packages/ocaml-variants/ocaml-variants.4.12.0+pr867+flambda2/opam b/packages/ocaml-variants/ocaml-variants.4.12.0+pr867+flambda2/opam
index 46bca58..69c3677 100644
--- a/packages/ocaml-variants/ocaml-variants.4.12.0+pr867+flambda2/opam
+++ b/packages/ocaml-variants/ocaml-variants.4.12.0+pr867+flambda2/opam
@@ -45,3 +45,4 @@ extra-source "alt-signal-stack.patch" {
   src: "https://github.com/ocaml/ocaml/commit/1eeb0e7fe595f5f9e1ea1edbdf785ff3b49feeeb.patch"
   checksum: "sha256=59de25b95409c1927c4b607fb4b1218ff7623fca45474448c8e114a42853e3ad"
 }
+extra-files: [ [ "ocaml-variants.config" "md5=2e903f01e0ca006dd7c6cc7e4ec4543f" ] ]