diff --git a/core/src/main/java/hudson/util/ProcessTreeKiller.java b/core/src/main/java/hudson/util/ProcessTreeKiller.java
index 040ff3cb288983708fc6eda279a777a883d9d75d..814d594b5a6513adf065c77232ab37c2a65b9835 100644
--- a/core/src/main/java/hudson/util/ProcessTreeKiller.java
+++ b/core/src/main/java/hudson/util/ProcessTreeKiller.java
@@ -94,6 +94,11 @@ public abstract class ProcessTreeKiller {
      *
      * <p>
      * The implementation is obviously OS-dependent.
+     *
+     * @param proc
+     *      Process to be killed recursively. Can be null.
+     * @param modelEnvVars
+     *      If non-null, search-and-destroy will be performed.
      */
     public abstract void kill(Process proc, Map<String, String> modelEnvVars);