diff --git a/pkgs/development/libraries/mailcore2/default.nix b/pkgs/development/libraries/mailcore2/default.nix
index 75e3439db81..d5f20f6761c 100644
--- a/pkgs/development/libraries/mailcore2/default.nix
+++ b/pkgs/development/libraries/mailcore2/default.nix
@@ -5,13 +5,13 @@
 stdenv.mkDerivation rec {
   pname = "mailcore2";
 
-  version = "0.6.3";
+  version = "0.6.4";
 
   src = fetchFromGitHub {
     owner  = "MailCore";
     repo   = "mailcore2";
     rev    = version;
-    sha256 = "0yxynvfmifpw9hdhv499a813hb2ynan74r353lhcdajkkm7w8br5";
+    sha256 = "0a69q11z194fdfwyazjyyylx57sqs9j4lz7jwh5qcws8syqgb23z";
   };
 
   nativeBuildInputs = [ pkgconfig ];