diff --git a/Crypto/Cipher/Types/AEAD.hs b/Crypto/Cipher/Types/AEAD.hs
index 4a4f613..ef306b0 100644
--- a/Crypto/Cipher/Types/AEAD.hs
+++ b/Crypto/Cipher/Types/AEAD.hs
@@ -27,7 +27,7 @@ data AEADModeImpl st = AEADModeImpl
 -- | Authenticated Encryption with Associated Data algorithms
 data AEAD cipher = forall st . AEAD
     { aeadModeImpl :: AEADModeImpl st
-    , aeadState    :: st
+    , aeadState    :: !st
     }
 
 -- | Append some header information to an AEAD context