diff --git a/package.json b/package.json
index 2fdf0c6..8f7c4d6 100644
--- a/package.json
+++ b/package.json
@@ -65,7 +65,7 @@
     "rollup-plugin-typescript2": "^0.19.0",
     "ts-jest": "24.0.0",
     "ts-node": "^8.0.3",
-    "tslint": "^5.9.1",
+    "tslint": "^5.13.0",
     "typescript": "^2.8.1"
   },
   "commitlint": {
diff --git a/src/transformer.ts b/src/transformer.ts
index 7a645c6..dda1d25 100644
--- a/src/transformer.ts
+++ b/src/transformer.ts
@@ -1,4 +1,4 @@
-import { ConstructorFor, Unknown, Nullable } from 'simplytyped';
+import { ConstructorFor, Nullable } from 'simplytyped';
 // @ts-ignore
 import Maybe, { MatchType, Nil } from './maybe';
 import { maybe } from './index';
@@ -22,10 +22,10 @@ const getMap = (x: MonadLike<any>): Monad<any>['map'] => {
     return x.map.bind(x) as any;
 };
 
-export class MaybeT<T extends MonadLike<Unknown>> {
+export class MaybeT<T extends MonadLike<unknown>> {
     private constructor(private value: T) {}
 
-    static maybeT<V extends MonadLike<Unknown>>(monad: V) {
+    static maybeT<V extends MonadLike<unknown>>(monad: V) {
         return new MaybeT(monad);
     }