diff --git a/README.md b/README.md
index 4a997ea..e4d3ab3 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,12 @@ In addition, I would like to thank Steve Vinoski, Rickard Green, and Sverker Eri
 
 ## v0.10.x
 
+### v0.10.x
+
+Maintenance release.
+
+* Fix type for `enacl:box_open/4`. The specification was wrong which results in errors in other applications using enacl.
+
 ### v0.10.2
 
 Maintenance release. Fix some usability problems with the library.
diff --git a/src/enacl.erl b/src/enacl.erl
index 8ff4089..3f11c9f 100644
--- a/src/enacl.erl
+++ b/src/enacl.erl
@@ -185,7 +185,7 @@ box(Msg, Nonce, PK, SK) ->
 %% Decrypt a `CipherText` into a `Msg` given the other partys public key `PK` and your secret
 %% key `SK`. Also requires the same nonce as was used by the other party. Returns the plaintext
 %% message.
--spec box_open(CipherText, Nonce, PK, SK) -> Msg
+-spec box_open(CipherText, Nonce, PK, SK) -> {ok, M} | {error, failed_verification}
   when CipherText :: iodata(),
        Nonce :: binary(),
        PK :: binary(),