diff --git a/web/src/channel.js b/web/src/channel.js
index f39e6923e7..1abd8310ca 100644
--- a/web/src/channel.js
+++ b/web/src/channel.js
@@ -112,9 +112,6 @@ function call(args) {
     return $.ajax(args);
 }
 
-// TODO: When this file is converted to TypeScript, deduplicate the
-// AjaxRequest type defined in dialog_widget.js.
-
 export function get(options) {
     const args = {type: "GET", dataType: "json", ...options};
     return call(args);
diff --git a/web/src/dialog_widget.ts b/web/src/dialog_widget.ts
index ed64168561..ec708b30bc 100644
--- a/web/src/dialog_widget.ts
+++ b/web/src/dialog_widget.ts
@@ -5,6 +5,7 @@ import render_dialog_widget from "../templates/dialog_widget.hbs";
 import {$t_html} from "./i18n";
 import * as loading from "./loading";
 import * as overlays from "./overlays";
+import type {AjaxRequestHandler} from "./types";
 import * as ui_report from "./ui_report";
 
 /*
@@ -61,24 +62,10 @@ type WidgetConfig = {
     loading_spinner?: boolean;
 };
 
-// TODO: This type should probably be exported from channel.ts once
-// that's converted to TypeScript.
-type AjaxRequest = ({
-    url,
-    data = {},
-    success,
-    error,
-}: {
-    url: string;
-    data?: Record<string, never>;
-    success(response_data?: string): void;
-    error(xhr?: JQuery.jqXHR): void;
-}) => void;
-
 type RequestOpts = {
     failure_msg_html?: string;
-    success_continuation?: (response_data?: string) => void;
-    error_continuation?: (xhr?: JQuery.jqXHR) => void;
+    success_continuation?: Parameters<AjaxRequestHandler>[0]["success"];
+    error_continuation?: Parameters<AjaxRequestHandler>[0]["error"];
 };
 
 export function hide_dialog_spinner(): void {
@@ -190,9 +177,9 @@ export function launch(conf: WidgetConfig): void {
 }
 
 export function submit_api_request(
-    request_method: AjaxRequest,
+    request_method: AjaxRequestHandler,
     url: string,
-    data = {},
+    data: Parameters<AjaxRequestHandler>[0]["data"] = {},
     {
         failure_msg_html = $t_html({defaultMessage: "Failed"}),
         success_continuation,
@@ -203,17 +190,17 @@ export function submit_api_request(
     request_method({
         url,
         data,
-        success(response_data?: string) {
+        success(response_data, textStatus, jqXHR) {
             close_modal();
             if (success_continuation !== undefined) {
-                success_continuation(response_data);
+                success_continuation(response_data, textStatus, jqXHR);
             }
         },
-        error(xhr?: JQuery.jqXHR) {
+        error(xhr, error_type, xhn) {
             ui_report.error(failure_msg_html, xhr, $("#dialog_error"));
             hide_dialog_spinner();
             if (error_continuation !== undefined) {
-                error_continuation(xhr);
+                error_continuation(xhr, error_type, xhn);
             }
         },
     });
diff --git a/web/src/types.ts b/web/src/types.ts
index dc14653c3a..78122d1db2 100644
--- a/web/src/types.ts
+++ b/web/src/types.ts
@@ -69,3 +69,12 @@ export type UpdateMessageEvent = {
 // TODO/typescript: Move the User and Stream placeholder
 // types to their appropriate modules.
 export type User = Record<string, never>;
+
+// TODO/typescript: Move this to channel
+export type AjaxRequestHandler = (args: {
+    url: string;
+    data?: Record<string, unknown> | string | unknown[];
+    ignoreReload?: boolean;
+    success?(response_data: unknown, textStatus: string, jqXHR: JQuery.jqXHR): void;
+    error?(xhr: JQuery.jqXHR, error_type: string, xhn: string): void;
+}) => void;