diff --git a/packages/wdio-browserstack-service/src/index.ts b/packages/wdio-browserstack-service/src/index.ts
index 32b65e41f1a..1168a667673 100644
--- a/packages/wdio-browserstack-service/src/index.ts
+++ b/packages/wdio-browserstack-service/src/index.ts
@@ -20,6 +20,9 @@ export * from './types.js'
 declare global {
     namespace WebdriverIO {
         interface ServiceOption extends BrowserstackConfig {}
+        interface Browser {
+            setCustomTags: (key: string, value: string) => Promise<void>
+        }
     }
     interface State {
         value: number,