diff --git a/MaterialDesignLibrary/MaterialDesign/src/main/java/com/gc/materialdesign/views/Slider.java b/MaterialDesignLibrary/MaterialDesign/src/main/java/com/gc/materialdesign/views/Slider.java
index 9fc435b..78e78ef 100644
--- a/MaterialDesignLibrary/MaterialDesign/src/main/java/com/gc/materialdesign/views/Slider.java
+++ b/MaterialDesignLibrary/MaterialDesign/src/main/java/com/gc/materialdesign/views/Slider.java
@@ -94,7 +94,9 @@ public void run() {
 
     @Override
     public void invalidate() {
-        ball.invalidate();
+        if (ball != null) {
+            ball.invalidate();
+        }
         super.invalidate();
     }