diff --git a/pikaday/pikaday.d.ts b/pikaday/pikaday.d.ts
index 3e4f80df9a..913ea69613 100644
--- a/pikaday/pikaday.d.ts
+++ b/pikaday/pikaday.d.ts
@@ -10,6 +10,14 @@ declare class Pikaday {
 
     constructor(options: Pikaday.PikadayOptions);
 
+    /**
+     * Extends the existing configuration options for Pikaday object with the options provided.
+     * Can be used to change/extend the configurations on runtime.
+     * @param options full/partial configuration options.
+     * @returns {} extended configurations.
+     */
+    config(options: Pikaday.PikadayOptions): Pikaday.PikadayOptions;
+
     /**
      * Returns the selected date in a string format. If Moment.js exists
      * (recommended) then Pikaday can return any format that Moment