diff --git a/c_src/generichash.c b/c_src/generichash.c
index a554d43..8f184a3 100644
--- a/c_src/generichash.c
+++ b/c_src/generichash.c
@@ -235,7 +235,6 @@ ERL_NIF_TERM enacl_crypto_generichash_update(ErlNifEnv *env, int argc,
     goto bad_arg;
 
   enif_mutex_lock(obj->mtx);
-
   if (!obj->alive) {
     goto err;
   }
@@ -251,7 +250,7 @@ ERL_NIF_TERM enacl_crypto_generichash_update(ErlNifEnv *env, int argc,
 bad_arg:
   return enif_make_badarg(env);
 err:
-  ret = enacl_internal_error(env);
+  ret = enacl_error_finalized(env);
 done:
   enif_mutex_unlock(obj->mtx);
   return ret;
@@ -271,7 +270,8 @@ ERL_NIF_TERM enacl_crypto_generichash_final(ErlNifEnv *env, int argc,
 
   enif_mutex_lock(obj->mtx);
   if (!obj->alive) {
-    goto bad_arg;
+    ret = enacl_error_finalized(env);
+    goto done;
   }
 
   if (!enif_alloc_binary(obj->outlen, &hash)) {
@@ -295,7 +295,7 @@ bad_arg:
 release:
   enif_release_binary(&hash);
 err:
-  ret = enif_make_badarg(env);
+  ret = enacl_internal_error(env);
 done:
   enif_mutex_unlock(obj->mtx);
   return ret;
diff --git a/test/enacl_SUITE.erl b/test/enacl_SUITE.erl
index 2d564d1..9d0adb6 100644
--- a/test/enacl_SUITE.erl
+++ b/test/enacl_SUITE.erl
@@ -83,6 +83,18 @@ generichash_chunked(_Config) ->
     Expected = <<46,49,32,18,13,186,182,105,106,122,253,139,89,176,169,141,
                  73,93,99,6,41,216,110,41>>,
     Expected = enacl:generichash_final(State),
+    try enacl:generichash_final(State) of
+        _ -> ct:fail(must_finalize)
+    catch
+        error:enacl_finalized ->
+            ok
+    end,
+    try enacl:generichash_update(State, <<"x">>) of
+        _ -> ct:fail(must_finalize)
+    catch
+        error:enacl_finalized ->
+            ok
+    end,
     ok.
 
 generichash_chunked(State, _Msg, 0) -> State;