diff --git a/src/main/java/org/apache/commons/collections4/bidimap/TreeBidiMap.java b/src/main/java/org/apache/commons/collections4/bidimap/TreeBidiMap.java
index 2697fa165f..13a3c2aa11 100644
--- a/src/main/java/org/apache/commons/collections4/bidimap/TreeBidiMap.java
+++ b/src/main/java/org/apache/commons/collections4/bidimap/TreeBidiMap.java
@@ -2224,12 +2224,12 @@ public Set<V> values() {
      * @param out the target ObjectOutputStream.
      * @throws IOException thrown when an I/O errors occur writing to the target stream.
      */
-    private void writeObject(final ObjectOutputStream stream) throws IOException {
-        stream.defaultWriteObject();
-        stream.writeInt(this.size());
+    private void writeObject(final ObjectOutputStream out) throws IOException {
+        out.defaultWriteObject();
+        out.writeInt(this.size());
         for (final Entry<K, V> entry : entrySet()) {
-            stream.writeObject(entry.getKey());
-            stream.writeObject(entry.getValue());
+            out.writeObject(entry.getKey());
+            out.writeObject(entry.getValue());
         }
     }