diff --git a/types/inquirer/index.d.ts b/types/inquirer/index.d.ts
index 90697f2423..9f23ad21aa 100644
--- a/types/inquirer/index.d.ts
+++ b/types/inquirer/index.d.ts
@@ -22,8 +22,12 @@ declare namespace inquirer {
         | Question<T>
         | ReadonlyArray<Question<T>>
         | Rx.Observable<Question<T>>;
-    type OutputStreamOption = {output: NodeJS.WritableStream};
-    type InputStreamOption = {input: NodeJS.ReadableStream};
+    interface OutputStreamOption {
+        output: NodeJS.WriteStream
+    }
+    interface InputStreamOption {
+        input: NodeJS.ReadStream
+    }
     type StreamOptions = InputStreamOption | OutputStreamOption | (InputStreamOption & OutputStreamOption);
 
     interface Inquirer {
@@ -38,7 +42,7 @@ declare namespace inquirer {
          * Create a new self-contained prompt module.
          * @param opt Object specifying input and output streams for the prompt
          */
-        createPromptModule(opt?: StreamOptions): PromptModule;
+        createPromptModule(opt?: OutputStreamOption): PromptModule;
         /**
          * Public CLI helper interface
          * @param questions Questions settings array