diff --git a/src/utils/delay.ts b/src/utils/delay.ts
index 809f177..24a4d2e 100644
--- a/src/utils/delay.ts
+++ b/src/utils/delay.ts
@@ -1,4 +1,4 @@
-export function delay<T = undefined>(ms: number, value?: T): Promise<T> {
+export function delay(ms: number, value?: undefined): Promise<undefined> {
    return new Promise((resolve) => {
       setTimeout(() => { resolve(value); }, ms);
    });
diff --git a/src/utils/is-enum-value.ts b/src/utils/is-enum-value.ts
index 12fa9c2..b57a45b 100644
--- a/src/utils/is-enum-value.ts
+++ b/src/utils/is-enum-value.ts
@@ -2,7 +2,7 @@
  * Type guard to check to see if the given value is a valid value for the enum.
  */
 export function isEnumValue<T>(enumType: T, value: unknown): value is T[keyof T] {
-   return (Object.keys(enumType) as Array<keyof T>)
+   return (Object.keys(enumType as {}) as Array<keyof T>)
       .map((key) => {
          return enumType[key];
       })
diff --git a/tests/utils/delay.test.ts b/tests/utils/delay.test.ts
index 09a470f..7693794 100644
--- a/tests/utils/delay.test.ts
+++ b/tests/utils/delay.test.ts
@@ -4,7 +4,7 @@ import { delay, isPromiseLike } from '../../src';
 describe('delay', () => {
 
    it('delays before returning a value', async () => {
-      let after: string | null = null,
+      let after: string | undefined | null = null,
           promise = delay(10, 'this-is-my-test-value');
 
       promise.then((v) => { after = v; });
diff --git a/tests/utils/is-empty.test.ts b/tests/utils/is-empty.test.ts
index 1ef823f..fc02a38 100644
--- a/tests/utils/is-empty.test.ts
+++ b/tests/utils/is-empty.test.ts
@@ -31,7 +31,7 @@ describe('isEmpty', () => {
       expect(t.isEmpty(() => {})).to.strictlyEqual(true);
 
       // deleting all the keys from on object empties it
-      o = { a: true };
+      o = { a: true } as { a?: boolean };
       expect(t.isEmpty(o)).to.strictlyEqual(false);
       delete o.a;
       expect(t.isEmpty(o)).to.strictlyEqual(true);