diff --git a/.ci-macosx.sh b/.ci-macosx.sh
index b793b0d7a..a27cf3415 100644
--- a/.ci-macosx.sh
+++ b/.ci-macosx.sh
@@ -2,15 +2,21 @@
 
 set -e
 
+sw_vers
+system_profiler SPSoftwareDataType
+uname -a
+
 brew update
 brew install pkg-config
 brew install opam
 brew install libev
-opam init -y --compiler=4.12.0
-eval $(opam env)
+brew install openssl
+opam init -y -a --bare
 
-opam install -y -j 2 . --deps-only --locked
-make && make opaminstall
+opam switch create . ocaml-base-compiler --deps-only --locked -y -j 2 # -v
+eval $(opam env)
+make
+make opaminstall
 
 # See src/main/linking_flags.sh
 make detect-libs
diff --git a/.github/workflows/static-builds.yml b/.github/workflows/static-builds.yml
index a87fffebd..9734914f7 100644
--- a/.github/workflows/static-builds.yml
+++ b/.github/workflows/static-builds.yml
@@ -8,6 +8,9 @@ on:
   pull_request:
     branches:
       - '**'
+  schedule:
+    # test master every Saturday at 08:00 UTC
+    - cron: '0 8 * * 6'
 jobs:
   static-bin-linux:
     name: Builds static Linux binaries
diff --git a/learn-ocaml-client.opam b/learn-ocaml-client.opam
index e32fa2879..19db6a0c9 100644
--- a/learn-ocaml-client.opam
+++ b/learn-ocaml-client.opam
@@ -29,7 +29,7 @@ depends: [
   "ezjsonm"
   "lwt" {>= "4.0.0"}
   "lwt_ssl"
-  "ocaml" {= "4.12.0"}
+  "ocaml" {(>= "4.12") & (< "4.13~")}
   "ocamlfind" {build}
   "ocp-indent-nlfork"
   "ocp-ocamlres" {>= "0.4"}
diff --git a/learn-ocaml-client.opam.locked b/learn-ocaml-client.opam.locked
index e6c67f20b..c900f21ed 100644
--- a/learn-ocaml-client.opam.locked
+++ b/learn-ocaml-client.opam.locked
@@ -67,7 +67,7 @@ depends: [
   "menhirSdk" {= "20210419"}
   "mmap" {= "1.1.0"}
   "num" {= "1.4"}
-  "ocaml" {= "4.12.0"}
+  "ocaml" {= "4.12.1"}
   "ocaml-compiler-libs" {= "v0.12.3"}
   "ocaml-config" {= "2"}
   "ocaml-migrate-parsetree" {= "1.8.0"}
diff --git a/learn-ocaml.opam b/learn-ocaml.opam
index c343c5a86..4e3173000 100644
--- a/learn-ocaml.opam
+++ b/learn-ocaml.opam
@@ -40,7 +40,7 @@ depends: [
   "magic-mime"
   "markup"
   "markup-lwt"
-  "ocaml" {= "4.12.0"}
+  "ocaml" {(>= "4.12") & (< "4.13~")}
   "ocamlfind" {build}
   "ocp-indent-nlfork"
   "ocp-ocamlres" {= "0.4"}
diff --git a/learn-ocaml.opam.locked b/learn-ocaml.opam.locked
index 40f7a6ef0..3426831e9 100644
--- a/learn-ocaml.opam.locked
+++ b/learn-ocaml.opam.locked
@@ -73,7 +73,7 @@ depends: [
   "menhirSdk" {= "20210419"}
   "mmap" {= "1.1.0"}
   "num" {= "1.4"}
-  "ocaml" {= "4.12.0"}
+  "ocaml" {= "4.12.1"}
   "ocaml-compiler-libs" {= "v0.12.3"}
   "ocaml-config" {= "2"}
   "ocaml-migrate-parsetree" {= "1.8.0"}
diff --git a/scripts/static-build.sh b/scripts/static-build.sh
index f336e7f2e..f854d6b17 100755
--- a/scripts/static-build.sh
+++ b/scripts/static-build.sh
@@ -10,7 +10,7 @@ cd $(dirname "$0")/..
 set -o pipefail
 git ls-files -z | xargs -0 tar c | \
   docker run --rm -i \
-    ocamlpro/ocaml:4.12-2021-07-25 \
+    ocamlpro/ocaml:4.12 \
     sh -uexc \
       'tar x >&2 &&
        sudo apk add openssl-libs-static bash >&2 &&