diff --git a/library/src/main/java/com/github/channguyen/rsv/RangeSliderView.java b/library/src/main/java/com/github/channguyen/rsv/RangeSliderView.java
index 4b8da6c..08e4f9f 100644
--- a/library/src/main/java/com/github/channguyen/rsv/RangeSliderView.java
+++ b/library/src/main/java/com/github/channguyen/rsv/RangeSliderView.java
@@ -256,7 +256,7 @@ private void preComputeDrawingPosition() {
   }
 
   public void setInitialIndex(int index) {
-    if (index < 0 || index > rangeCount) {
+    if (index < 0 || index >= rangeCount) {
       throw new IllegalArgumentException("Attempted to set index=" + index + " out of range [0," + rangeCount + "]");
     }
     currentIndex = index;