diff --git a/flexSlider/flexSlider.d.ts b/flexSlider/flexSlider.d.ts
index c8fa3f949c..276bb35e84 100644
--- a/flexSlider/flexSlider.d.ts
+++ b/flexSlider/flexSlider.d.ts
@@ -78,10 +78,10 @@ interface FlexSliderOptions {
 	// Callback API
 	start?: (slider: SliderObject) => any;            //Callback: function(slider) - Fires when the slider loads the first slide
 	before?: (slider: SliderObject) => any;           //Callback: function(slider) - Fires asynchronously with each slider animation
-	after?: () => any;            //Callback: function(slider) - Fires after each slider animation completes
-	end?: () => any;              //Callback: function(slider) - Fires when the slider reaches the last slide (asynchronous)
-	added?: () => any;            //{NEW} Callback: function(slider) - Fires after a slide is added
-	removed?: () => any;
+	after?: (slider: SliderObject) => any;            //Callback: function(slider) - Fires after each slider animation completes
+	end?: (slider: SliderObject) => any;              //Callback: function(slider) - Fires when the slider reaches the last slide (asynchronous)
+	added?: (slider: SliderObject) => any;            //{NEW} Callback: function(slider) - Fires after a slide is added
+	removed?: (slider: SliderObject) => any;
 }