diff --git a/src/main/java/htsjdk/samtools/util/Lazy.java b/src/main/java/htsjdk/samtools/util/Lazy.java
index b42ec7c2c..13726b878 100644
--- a/src/main/java/htsjdk/samtools/util/Lazy.java
+++ b/src/main/java/htsjdk/samtools/util/Lazy.java
@@ -28,6 +28,7 @@ public synchronized T get() {
     }
 
     /** Describes how to build the instance of the lazy object. */
+    @FunctionalInterface
     public interface LazyInitializer<T> {
         /** Returns the desired object instance. */
         T make();