diff --git a/mirage-crypto-rng-eio.opam b/mirage-crypto-rng-eio.opam
index 6348bb0e..522e0eff 100644
--- a/mirage-crypto-rng-eio.opam
+++ b/mirage-crypto-rng-eio.opam
@@ -20,6 +20,7 @@ depends: [
   "mirage-crypto-rng" {=version}
   "duration"
   "mtime"
+  "cstruct" {>= "6.1.0"}
   "eio_main" {with-test}
   "ohex" {with-test & >= "0.2.0"}
 ]
diff --git a/rng/eio/dune b/rng/eio/dune
index d268ef83..44df0317 100644
--- a/rng/eio/dune
+++ b/rng/eio/dune
@@ -1,4 +1,4 @@
 (library
  (name mirage_crypto_rng_eio)
  (public_name mirage-crypto-rng-eio)
- (libraries eio logs mirage-crypto-rng duration mtime))
+ (libraries eio logs mirage-crypto-rng duration mtime cstruct))
diff --git a/tests/test_rng.ml b/tests/test_rng.ml
deleted file mode 100644
index 87615c8f..00000000
--- a/tests/test_rng.ml
+++ /dev/null
@@ -1,26 +0,0 @@
-
-let all0 cs =
-  let c = ref 0 in
-  let l = Cstruct.length cs in
-  for i = 0 to pred l do
-    if Cstruct.get_uint8 cs i = 0 then incr c
-  done;
-  l = !c
-
-let () =
-  Printf.printf "foo\n%!";
-  Mirage_crypto_rng_unix.initialize (module Mirage_crypto_rng.Fortuna);
-  let rec one z n = function
-    | 0 -> z
-    | c ->
-      let data = Mirage_crypto_rng.generate n in
-      Cstruct.hexdump data;
-      let z' = if all0 data then succ z else z in
-      one z' n (pred c)
-  in
-  let iterations = 1_000 in
-  let all0 = one 0 260 iterations in
-  if all0 = iterations then
-    Printf.printf "all 0\n"
-  else
-    Printf.printf "%d iterations\n" iterations