diff --git a/packages/calculon/calculon.0.5/opam b/packages/calculon/calculon.0.5/opam
index 1e05951b9f6..b3f143ace27 100644
--- a/packages/calculon/calculon.0.5/opam
+++ b/packages/calculon/calculon.0.5/opam
@@ -16,7 +16,7 @@ depends: [
   "irc-client" { >= "0.6.0" & < "0.7.0" }
   "irc-client-lwt"
   "irc-client-lwt-ssl"
-  "yojson" {>= "1.4.1"}
+  "yojson" {>= "1.4.1" & < "2.0.0"}
   "containers" { >= "1.2" & < "3.0" }
   "ISO8601"
   "stringext"
diff --git a/packages/merlin/merlin.4.5-414/opam b/packages/merlin/merlin.4.5-414/opam
index bef6f2d72d4..2c9a345eb3c 100644
--- a/packages/merlin/merlin.4.5-414/opam
+++ b/packages/merlin/merlin.4.5-414/opam
@@ -14,7 +14,7 @@ depends: [
   "ocaml" {>= "4.14" & < "4.15"}
   "dune" {>= "2.9.0"}
   "dot-merlin-reader" {>= "4.2"}
-  "yojson" {>= "1.6.0"}
+  "yojson" {>= "1.6.0" & < "2.0.0"}
   "conf-jq" {with-test}
   "csexp" {>= "1.5.1"}
   "menhir" {dev}