diff --git a/ca-certs.opam b/ca-certs.opam
index 54a6d4b..ff0dde6 100644
--- a/ca-certs.opam
+++ b/ca-certs.opam
@@ -20,8 +20,8 @@ depends: [
   "fpath"
   "ptime"
   "logs"
-  "mirage-crypto"
-  "x509" {>= "0.13.0"}
+  "mirage-crypto" {< "1.0.0"}
+  "x509" {>= "0.13.0" & < "1.0.0"}
   "ocaml" {>= "4.08.0"}
   "alcotest" {with-test}
   "fmt" {with-test & >= "0.8.7"}
diff --git a/dune-project b/dune-project
index be59bf0..948e2c9 100644
--- a/dune-project
+++ b/dune-project
@@ -11,8 +11,9 @@
 (package
  (name ca-certs)
  (depends
-  bos fpath ptime logs mirage-crypto
-  (x509 (>= 0.13.0))
+  bos fpath ptime logs
+  (mirage-crypto (< 1.0.0))
+  (x509 (and (>= 0.13.0) (< 1.0.0)))
   (ocaml (>= 4.08.0))
   (alcotest :with-test)
   (fmt (and :with-test (>= 0.8.7))))