diff --git a/app/src/main/java/com/wireguard/android/ObservableSortedMap.java b/app/src/main/java/com/wireguard/android/ObservableSortedMap.java
index 8a642476..5c96c68c 100644
--- a/app/src/main/java/com/wireguard/android/ObservableSortedMap.java
+++ b/app/src/main/java/com/wireguard/android/ObservableSortedMap.java
@@ -9,4 +9,5 @@ import java.util.SortedMap;
  */
 
 public interface ObservableSortedMap<K, V> extends ObservableMap<K, V>, SortedMap<K, V> {
+    // No additional methods.
 }