diff --git a/tools/test-js-with-node b/tools/test-js-with-node
index a3cfc46618..89b1e5c7dc 100755
--- a/tools/test-js-with-node
+++ b/tools/test-js-with-node
@@ -76,7 +76,7 @@ EXEMPT_FILES = make_set(
         "web/src/copy_and_paste.js",
         "web/src/csrf.ts",
         "web/src/css_variables.js",
-        "web/src/dark_theme.js",
+        "web/src/dark_theme.ts",
         "web/src/debug.ts",
         "web/src/deprecated_feature_notice.js",
         "web/src/desktop_integration.js",
diff --git a/web/src/dark_theme.js b/web/src/dark_theme.ts
similarity index 83%
rename from web/src/dark_theme.js
rename to web/src/dark_theme.ts
index 9b9ef2e942..c92f7e5886 100644
--- a/web/src/dark_theme.js
+++ b/web/src/dark_theme.ts
@@ -3,7 +3,7 @@ import $ from "jquery";
 import {localstorage} from "./localstorage";
 import {page_params} from "./page_params";
 
-export function enable() {
+export function enable(): void {
     $(":root").removeClass("color-scheme-automatic").addClass("dark-theme");
 
     if (page_params.is_spectator) {
@@ -12,7 +12,7 @@ export function enable() {
     }
 }
 
-export function disable() {
+export function disable(): void {
     $(":root").removeClass("color-scheme-automatic").removeClass("dark-theme");
 
     if (page_params.is_spectator) {
@@ -21,6 +21,6 @@ export function disable() {
     }
 }
 
-export function default_preference_checker() {
+export function default_preference_checker(): void {
     $(":root").removeClass("dark-theme").addClass("color-scheme-automatic");
 }