diff --git a/types/config.d.ts b/types/config.d.ts
index 97c4dfd9c4f7..ef2a8f4bc35b 100644
--- a/types/config.d.ts
+++ b/types/config.d.ts
@@ -218,6 +218,9 @@ interface ThemeConfig {
   transitionDuration: ResolvableTo<KeyValuePair>
   willChange: ResolvableTo<KeyValuePair>
   content: ResolvableTo<KeyValuePair>
+
+  /** Custom */
+  [key: string]: any
 }
 
 // Core plugins related config