diff --git a/types/webdriverio/index.d.ts b/types/webdriverio/index.d.ts
index ea34a6c034..a3d7a08d99 100644
--- a/types/webdriverio/index.d.ts
+++ b/types/webdriverio/index.d.ts
@@ -421,7 +421,7 @@ declare namespace WebdriverIO {
         mochaOpts?: { [name: string]: any; };
         jasmineNodeOpts?: { [name: string]: any; };
         cucumberOpts?: { [name: string]: any; };
-        services?: string | ((...args: any[]) => void);
+        services?: string[] | ((...args: any[]) => void);
         screenshotPath?: string;
         specs?: string[];
         seleniumLogs?: string;