diff --git a/solo5-elftool.opam b/solo5-elftool.opam
index 9dfc523..40661e0 100644
--- a/solo5-elftool.opam
+++ b/solo5-elftool.opam
@@ -14,10 +14,10 @@ build: [
 ]
 
 depends: [
-  "ocaml"
+  "ocaml" {>= "4.8.0"}
   "dune" {>= "2.9"}
   "owee" {>= "0.4"}
-  "cstruct"
+  "cstruct" {>= "6.0.0"}
   "fmt" {>= "0.8.7"}
   "cmdliner"
 ]