diff --git a/capnp-rpc-lwt.opam b/capnp-rpc-lwt.opam
index ed56501b..06489215 100644
--- a/capnp-rpc-lwt.opam
+++ b/capnp-rpc-lwt.opam
@@ -11,13 +11,13 @@ homepage: "https://github.com/mirage/capnp-rpc"
 bug-reports: "https://github.com/mirage/capnp-rpc/issues"
 doc: "https://mirage.github.io/capnp-rpc/"
 depends: [
-  "ocaml" {>= "4.03.0"}
+  "ocaml" {>= "4.08.0"}
   "conf-capnproto" {build}
   "capnp" {>= "3.4.0"}
   "capnp-rpc" {= version}
   "lwt"
   "astring"
-  "fmt"
+  "fmt" {>= "0.8.7"}
   "logs"
   "asetmap"
   "uri" {>= "1.6.0"}
diff --git a/capnp-rpc.opam b/capnp-rpc.opam
index a835730f..aef17df0 100644
--- a/capnp-rpc.opam
+++ b/capnp-rpc.opam
@@ -12,7 +12,7 @@ homepage: "https://github.com/mirage/capnp-rpc"
 bug-reports: "https://github.com/mirage/capnp-rpc/issues"
 doc: "https://mirage.github.io/capnp-rpc/"
 depends: [
-  "ocaml" {>= "4.03.0"}
+  "ocaml" {>= "4.08.0"}
   "stdint"
   "astring"
   "fmt"