diff --git a/README.md b/README.md
index b42bc40..5a48c4b 100644
--- a/README.md
+++ b/README.md
@@ -108,7 +108,7 @@ Each validation function accepts an (optional) object with the following attribu
 - `desc` - A string that describes the env var.
 - `example` - An example value for the env var.
 - `docs` - A URL that leads to more detailed documentation about the env var.
-- `requiredWhen` - A boolean function that specify when the env var is required. Use With default: undefined (optional value).
+- `requiredWhen` - A function (env -> boolean) specifying when this env var is required. Use With default: undefined (optional value).
 
 ## Custom validators
 
diff --git a/src/core.ts b/src/core.ts
index ea6fbb5..38c6a62 100644
--- a/src/core.ts
+++ b/src/core.ts
@@ -36,7 +36,7 @@ function validateVar<T>({
 }
 
 // Format a string error message for when a required env var is missing
-function formatSpecDescription<T>(spec: Spec<T>) {
+export function formatSpecDescription<T>(spec: Spec<T>) {
   const egText = spec.example ? ` (eg. "${spec.example}")` : ''
   const docsText = spec.docs ? `. See ${spec.docs}` : ''
   return `${spec.desc}${egText}${docsText}`
@@ -100,6 +100,8 @@ export function getSanitizedEnv<S>(
     }
   }
 
+  // This block is for supporting requiredWhen. If that field was provided for a var's spec and 
+  // its condition evaluates to a truthy value, ensure that env var is present.
   for (const k of varKeys) {
     if (errors[k] == undefined) {
       const spec = castedSpecs[k]
diff --git a/src/types.ts b/src/types.ts
index cc0f772..50e62b6 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -25,7 +25,11 @@ export interface Spec<T> {
    */
   devDefault?: NonNullable<T> | undefined
 
-  requiredWhen?: (cleanedEnv: any) => boolean | undefined
+  /**
+   * A function (env -> boolean) that allows an env var to be required only when certain
+   * conditions are met with the rest of the env object. Use With default: undefined.
+   */
+  requiredWhen?: (cleanedEnv: Record<string, unknown>) => boolean | undefined
 }
 
 type OptionalAttrs<T> =
@@ -103,16 +107,16 @@ export type SpecsOutput<S> = {
 
 export type CleanedEnv<S> =
   S extends Record<string, ValidatorSpec<unknown>>
-    ? Readonly<
-        {
-          [K in keyof S]: S[K] extends OptionalValidatorSpec<infer U>
-            ? U | undefined
-            : S[K] extends RequiredValidatorSpec<infer U>
-              ? U
-              : never
-        } & CleanedEnvAccessors
-      >
-    : never
+  ? Readonly<
+    {
+      [K in keyof S]: S[K] extends OptionalValidatorSpec<infer U>
+      ? U | undefined
+      : S[K] extends RequiredValidatorSpec<infer U>
+      ? U
+      : never
+    } & CleanedEnvAccessors
+  >
+  : never
 
 export interface CleanedEnvAccessors {
   /** true if NODE_ENV === 'development' */
diff --git a/tests/requiredWhen.test.ts b/tests/requiredWhen.test.ts
index 0142b1b..be9a11a 100644
--- a/tests/requiredWhen.test.ts
+++ b/tests/requiredWhen.test.ts
@@ -1,14 +1,11 @@
-// let defaultReporter: jest.Mock = jest.fn().mockImplementation(() => {})
-// jest.mock('../src/reporter.ts', () => {
-//   return {
-//     defaultReporter: defaultReporter,
-//   }
-// })
-import { bool, cleanEnv, defaultReporter, EnvMissingError, Spec, num, EnvError } from '../src'
+import { bool, cleanEnv, defaultReporter, EnvMissingError, num, EnvError } from '../src'
+import { formatSpecDescription } from '../src/core'
+
 jest.mock('../src/reporter')
-const mockedDefaultReporter: jest.Mock = <jest.Mock<typeof defaultReporter>> defaultReporter;
-mockedDefaultReporter.mockImplementation((a) => {console.log(a)})
-describe('required when', () => {
+const mockedDefaultReporter: jest.Mock = <jest.Mock<typeof defaultReporter>>defaultReporter;
+mockedDefaultReporter.mockImplementation(() => { })
+
+describe('requiredWhen', () => {
   beforeEach(() => {
     mockedDefaultReporter.mockClear()
   })
@@ -35,7 +32,7 @@ describe('required when', () => {
     })
   })
 
-  test("required but not provided", () => {
+  test('required but not provided', () => {
     cleanEnv(
       {
         autoExtractId: "false",
@@ -67,7 +64,7 @@ describe('required when', () => {
     })
   })
 
-  test("required and provided", () => {
+  test('required and provided', () => {
     cleanEnv(
       {
         autoExtractId: "false",
@@ -90,8 +87,8 @@ describe('required when', () => {
       errors: {},
     })
   })
-  
-  test("required but failed to parse", () => {
+
+  test('required but failed to parse', () => {
     cleanEnv(
       {
         autoExtractId: "false",
@@ -117,8 +114,3 @@ describe('required when', () => {
     })
   })
 })
-function formatSpecDescription<T>(spec: Spec<T>) {
-  const egText = spec.example ? ` (eg. "${spec.example}")` : ''
-  const docsText = spec.docs ? `. See ${spec.docs}` : ''
-  return `${spec.desc}${egText}${docsText}`
-}