diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/BaseDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/BaseDataSource.java
index 18a7dcea49..5ed2e33d2b 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/BaseDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/BaseDataSource.java
@@ -47,8 +47,10 @@ public abstract class BaseDataSource implements DataSource {
 
   @Override
   public final void addTransferListener(TransferListener transferListener) {
-    listeners.add(transferListener);
-    listenerCount++;
+    if (!listeners.contains(transferListener)) {
+      listeners.add(transferListener);
+      listenerCount++;
+    }
   }
 
   /**