diff --git a/core/src/main/java/hudson/model/Computer.java b/core/src/main/java/hudson/model/Computer.java
index d47ec824474d3ce8a12aef35fbf893a0f99682c7..86fbb6c0ea5381728f2c07a32c11571092f73e97 100644
--- a/core/src/main/java/hudson/model/Computer.java
+++ b/core/src/main/java/hudson/model/Computer.java
@@ -918,7 +918,7 @@ public /*transient*/ abstract class Computer extends Actionable implements Acces
      * @see ProcStarter#envs(Map)
      * @since 1.489
      */
-    public EnvVars buildEnvironment(TaskListener listener) throws IOException, InterruptedException {
+    public @Nonnull EnvVars buildEnvironment(@Nonnull TaskListener listener) throws IOException, InterruptedException {
         EnvVars env = new EnvVars();
 
         Node node = getNode();
diff --git a/core/src/main/java/hudson/model/EnvironmentContributor.java b/core/src/main/java/hudson/model/EnvironmentContributor.java
index 37084b10cbcfa40c203f048aab69d63e86b84a63..cbe05353d70ed5920a9f0edeb9bb72cf8f134b97 100644
--- a/core/src/main/java/hudson/model/EnvironmentContributor.java
+++ b/core/src/main/java/hudson/model/EnvironmentContributor.java
@@ -31,6 +31,7 @@ import hudson.scm.SCM;
 import jenkins.model.Jenkins;
 
 import java.io.IOException;
+import javax.annotation.Nonnull;
 
 /**
  * Contributes environment variables to builds.
@@ -79,14 +80,14 @@ public abstract class EnvironmentContributor implements ExtensionPoint {
      * variables that are scoped to builds.
      *
      * @param r
-     *      Build that's being performed. Never null.
+     *      Build that's being performed.
      * @param envs
      *      Partially built environment variable map. Implementation of this method is expected to
-     *      add additional variables here. Never null.
+     *      add additional variables here.
      * @param listener
-     *      Connected to the build console. Can be used to report errors. Never null.
+     *      Connected to the build console. Can be used to report errors.
      */
-    public void buildEnvironmentFor(Run r, EnvVars envs, TaskListener listener) throws IOException, InterruptedException {}
+    public void buildEnvironmentFor(@Nonnull Run r, @Nonnull EnvVars envs, @Nonnull TaskListener listener) throws IOException, InterruptedException {}
 
     /**
      * Contributes environment variables used for a job.
@@ -103,12 +104,12 @@ public abstract class EnvironmentContributor implements ExtensionPoint {
      *      Job for which some activities are launched.
      * @param envs
      *      Partially built environment variable map. Implementation of this method is expected to
-     *      add additional variables here. Never null.
+     *      add additional variables here.
      * @param listener
-     *      Connected to the build console. Can be used to report errors. Never null.
+     *      Connected to the build console. Can be used to report errors.
      * @since 1.527
      */
-    public void buildEnvironmentFor(Job j, EnvVars envs, TaskListener listener) throws IOException, InterruptedException {}
+    public void buildEnvironmentFor(@Nonnull Job j, @Nonnull EnvVars envs, @Nonnull TaskListener listener) throws IOException, InterruptedException {}
 
     /**
      * Returns all the registered {@link EnvironmentContributor}s.
diff --git a/core/src/main/java/hudson/model/Job.java b/core/src/main/java/hudson/model/Job.java
index 8818c9e764ee3c6be456ff649f43eb3348bc4965..31b3024f70e10c5bd350f2c68a57126f15915791 100644
--- a/core/src/main/java/hudson/model/Job.java
+++ b/core/src/main/java/hudson/model/Job.java
@@ -96,6 +96,8 @@ import java.io.*;
 import java.net.URLEncoder;
 import java.util.*;
 import java.util.List;
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
 
 import static javax.servlet.http.HttpServletResponse.*;
 import jenkins.model.lazy.LazyBuildMixIn;
@@ -356,7 +358,7 @@ public abstract class Job<JobT extends Job<JobT, RunT>, RunT extends Run<JobT, R
      *      Node to eventually run a process on. The implementation must cope with this parameter being null
      *      (in which case none of the node specific properties would be reflected in the resulting override.)
      */
-    public EnvVars getEnvironment(Node node, TaskListener listener) throws IOException, InterruptedException {
+    public @Nonnull EnvVars getEnvironment(@CheckForNull Node node, @Nonnull TaskListener listener) throws IOException, InterruptedException {
         EnvVars env;
 
         if (node!=null) {
diff --git a/core/src/main/java/hudson/model/Run.java b/core/src/main/java/hudson/model/Run.java
index 494868e331f72b99725c09467e7765b39b15be6f..9b9b88bc1064b6490a496fdb07e2e73e2f723b23 100644
--- a/core/src/main/java/hudson/model/Run.java
+++ b/core/src/main/java/hudson/model/Run.java
@@ -2206,10 +2206,10 @@ public abstract class Run <JobT extends Job<JobT,RunT>,RunT extends Run<JobT,Run
      * Unlike earlier {@link #getEnvVars()}, this map contains the whole environment,
      * not just the overrides, so one can introspect values to change its behavior.
      * 
-     * @return the map with the environmental variables. Never <code>null</code>.
+     * @return the map with the environmental variables.
      * @since 1.305
      */
-    public EnvVars getEnvironment(TaskListener listener) throws IOException, InterruptedException {
+    public @Nonnull EnvVars getEnvironment(@Nonnull TaskListener listener) throws IOException, InterruptedException {
         Computer c = Computer.currentComputer();
         Node n = c==null ? null : c.getNode();
 
diff --git a/core/src/main/java/hudson/slaves/NodeProperty.java b/core/src/main/java/hudson/slaves/NodeProperty.java
index 828f0ac9055f279f44c57f8edc2b042dfe6735ef..42da21efeb8fcfa860b91f74e15d116e94733123 100644
--- a/core/src/main/java/hudson/slaves/NodeProperty.java
+++ b/core/src/main/java/hudson/slaves/NodeProperty.java
@@ -39,6 +39,7 @@ import hudson.model.BuildListener;
 import hudson.model.Environment;
 import jenkins.model.Jenkins;
 import hudson.model.Node;
+import hudson.model.Queue;
 import hudson.model.Queue.Task;
 import net.sf.json.JSONObject;
 import org.kohsuke.stapler.StaplerRequest;
@@ -47,6 +48,7 @@ import java.io.File;
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
+import javax.annotation.Nonnull;
 
 /**
  * Extensible property of {@link Node}.
@@ -161,7 +163,7 @@ public abstract class NodeProperty<N extends Node> implements ReconfigurableDesc
      *
      * @since 1.489
      */
-    public void buildEnvVars(EnvVars env, TaskListener listener) throws IOException,InterruptedException {
+    public void buildEnvVars(@Nonnull EnvVars env, @Nonnull TaskListener listener) throws IOException,InterruptedException {
         // default is no-op
     }