diff --git a/inquirer/inquirer.d.ts b/inquirer/inquirer.d.ts
index 2abd6e6d53..c0f45a58ba 100644
--- a/inquirer/inquirer.d.ts
+++ b/inquirer/inquirer.d.ts
@@ -32,7 +32,7 @@ declare module "inquirer" {
              * @param cb Callback being passed the user answers
              * @return
              */
-            prompt(questions: Questions, cb?: (answers: Answers) => any): ui.Prompt;
+            prompt(questions: Questions, cb: (answers: Answers) => any): ui.Prompt;
             prompt(questions: Questions): Promise<Answers>;
             prompts: Prompts;
             Separator: objects.SeparatorStatic;