diff --git a/projects/Chart/5/org/jfree/data/xy/XYSeries.java b/projects/Chart/5/org/jfree/data/xy/XYSeries.java
index 0b37e6e..b26e11e 100644
--- a/projects/Chart/5/org/jfree/data/xy/XYSeries.java
+++ b/projects/Chart/5/org/jfree/data/xy/XYSeries.java
@@ -541,11 +541,15 @@ public XYDataItem addOrUpdate(Number x, Number y) {
         if (x == null) {
             throw new IllegalArgumentException("Null 'x' argument.");
         }
+        if (this.allowDuplicateXValues) {
+            add(x, y);
+            return null;
+        }
 
         // if we get to here, we know that duplicate X values are not permitted
         XYDataItem overwritten = null;
         int index = indexOf(x);
-        if (index >= 0 && !this.allowDuplicateXValues) {
+        if (index >= 0) {
             XYDataItem existing = (XYDataItem) this.data.get(index);
             try {
                 overwritten = (XYDataItem) existing.clone();