diff --git a/irmin.opam b/irmin.opam
index 0ae924ed2c..ed692691ae 100644
--- a/irmin.opam
+++ b/irmin.opam
@@ -22,8 +22,8 @@ depends: [
   "uutf"
   "jsonm"   {>= "1.0.0"}
   "eio"     {>= "0.12"}
-  "kcas"    {>= "0.6.1"}
-  "kcas_data" {>= "0.6.1"}
+  "kcas"    {= "dev"}
+  "kcas_data" {= "dev"}
   "lwt"     {>= "5.6.1"}
   "digestif" {>= "0.9.0"}
   "ocamlgraph"
@@ -44,7 +44,8 @@ depends: [
 
 pin-depends: [
   # Fix segv in kcas
-  [ "kcas.dev" "git+https://git@github.com/ocaml-multicore/kcas#5f3a39dfc72189e2b83f96c3754d402d5e7d6bc5"]
+  [ "kcas.dev" "git+https://git@github.com/ocaml-multicore/kcas#debeae67a48743f9659471a4de3b9166afdb1647"]
+  [ "kcas_data.dev" "git+https://git@github.com/ocaml-multicore/kcas#debeae67a48743f9659471a4de3b9166afdb1647"]
   # Metrics may have been unnecessarily constrained in opam-repository
   [ "metrics.dev" "git+https://github.com/mirage/metrics#995eb18d2837df02c8ead719c00fb156cf475ab5"]
   [ "metrics-unix.dev" "git+https://github.com/mirage/metrics#995eb18d2837df02c8ead719c00fb156cf475ab5"]