diff --git a/opam b/opam
index 039e948c..5f954178 100644
--- a/opam
+++ b/opam
@@ -23,7 +23,7 @@ depends: [
   "topkg" {build}
   "result"
   "cstruct" {>= "1.6.0"}
-  "sexplib"
+  "sexplib" {< "v0.11.0"}
   "asn1-combinators" {>= "0.2.0"}
   "ptime"
   "nocrypto" {>= "0.5.3"}