diff --git a/bootstrap.datepicker/bootstrap.datepicker.d.ts b/bootstrap.datepicker/bootstrap.datepicker.d.ts
index 686cc6b423..f60a0ffed6 100644
--- a/bootstrap.datepicker/bootstrap.datepicker.d.ts
+++ b/bootstrap.datepicker/bootstrap.datepicker.d.ts
@@ -15,7 +15,7 @@
  *  http://bootstrap-datepicker.readthedocs.org/en/release/options.html
  */
 interface DatepickerOptions {
-    format?: string;
+    format?: string | DatepickerCustomFormatOptions;
     weekStart?: number;
     startDate?: any;
     endDate?: any;
@@ -38,6 +38,11 @@ interface DatepickerOptions {
     assumeNearbyYear?: any;
 }
 
+interface DatepickerCustomFormatOptions {
+    toDisplay?(date: string, format: any, language: any): string;
+    toValue?(date: string, format: any, language: any): Date;
+}
+
 interface DatepickerEventObject extends JQueryEventObject {
     date: Date;
     format(format?: string): string;