diff --git a/experimental/uloapi/src/main/java/info/mathhub/uloapi/query/GraphDB.java b/experimental/uloapi/src/main/java/info/mathhub/uloapi/query/GraphDB.java
index 7d3983d1d67fa76cd468f0ec99040134e8e66067..3ce11cad9deccf007add93c64a5ea9b5ff60d6be 100644
--- a/experimental/uloapi/src/main/java/info/mathhub/uloapi/query/GraphDB.java
+++ b/experimental/uloapi/src/main/java/info/mathhub/uloapi/query/GraphDB.java
@@ -22,6 +22,8 @@ public class GraphDB {
     /**
      * Functional interface that defines a function for running operations on
      * a GraphDB database.
+     *
+     * @param <T> Return type of the operation.
      */
     public interface Operation<T> {
         /**