diff --git a/packages/aws-s3/aws-s3.0.9.0/opam b/packages/aws-s3/aws-s3.0.9.0/opam
index fe9d6eb9dcca..a7b6a8bdd5ce 100644
--- a/packages/aws-s3/aws-s3.0.9.0/opam
+++ b/packages/aws-s3/aws-s3.0.9.0/opam
@@ -20,6 +20,7 @@ depends: [
   "core" {< "v0.12"}
   "async" {< "v0.9"}
   "ounit"
+  "base64" {<"3.0.0"}
   "cohttp" {< "0.99"}
   "ocaml-inifiles"
   "cryptokit"
diff --git a/packages/aws-s3/aws-s3.1.1.0/opam b/packages/aws-s3/aws-s3.1.1.0/opam
index e38a512e142c..877057ea4a8e 100644
--- a/packages/aws-s3/aws-s3.1.1.0/opam
+++ b/packages/aws-s3/aws-s3.1.1.0/opam
@@ -12,6 +12,7 @@ depends: [
   "core" {>= "v0.9" & < "v0.10"}
   "async" {< "v0.12"}
   "async_extended"
+  "base64" {<"3.0.0"}
   "ounit"
   "cohttp-async"
   "ocaml-inifiles"
diff --git a/packages/aws-s3/aws-s3.1.1.1/opam b/packages/aws-s3/aws-s3.1.1.1/opam
index b3da3d08ac24..f0afe551c3f7 100644
--- a/packages/aws-s3/aws-s3.1.1.1/opam
+++ b/packages/aws-s3/aws-s3.1.1.1/opam
@@ -12,6 +12,7 @@ depends: [
   "core" {>= "v0.9" & < "v0.10"}
   "async" {< "v0.12"}
   "async_extended"
+  "base64" {<"3.0.0"}
   "ounit"
   "cohttp-async"
   "ocaml-inifiles"
diff --git a/packages/aws-s3/aws-s3.2.0.0/opam b/packages/aws-s3/aws-s3.2.0.0/opam
index 401846202bc6..478035bce73c 100644
--- a/packages/aws-s3/aws-s3.2.0.0/opam
+++ b/packages/aws-s3/aws-s3.2.0.0/opam
@@ -16,6 +16,7 @@ depends: [
   "core" {>= "v0.9.0" & < "v0.12"}
   "ounit"
   "cohttp"
+  "base64" {<"3.0.0"}
   "ocaml-inifiles"
   "cryptokit"
   "nocrypto"
diff --git a/packages/aws-s3/aws-s3.3.0.0/opam b/packages/aws-s3/aws-s3.3.0.0/opam
index 1dbedd059072..b5a2d8be2d72 100644
--- a/packages/aws-s3/aws-s3.3.0.0/opam
+++ b/packages/aws-s3/aws-s3.3.0.0/opam
@@ -14,6 +14,7 @@ depends: [
   "jbuilder" {build}
   "core" {>= "v0.9.0" & < "v0.12"}
   "ounit"
+  "base64" {<"3.0.0"}
   "cohttp"
   "ocaml-inifiles"
   "digestif" {<= "0.5"}