diff --git a/src/main/java/org/apache/commons/lang3/concurrent/BackgroundInitializer.java b/src/main/java/org/apache/commons/lang3/concurrent/BackgroundInitializer.java
index 57fac11a8..a47b35382 100644
--- a/src/main/java/org/apache/commons/lang3/concurrent/BackgroundInitializer.java
+++ b/src/main/java/org/apache/commons/lang3/concurrent/BackgroundInitializer.java
@@ -86,13 +86,13 @@ import java.util.concurrent.Future;
 public abstract class BackgroundInitializer<T> implements
         ConcurrentInitializer<T> {
     /** The external executor service for executing tasks. */
-    private ExecutorService externalExecutor;
+    private ExecutorService externalExecutor; // @GuardedBy("this")
 
     /** A reference to the executor service that is actually used. */
-    private ExecutorService executor;
+    private ExecutorService executor; // @GuardedBy("this")
 
     /** Stores the handle to the background task. */
-    private Future<T> future;
+    private Future<T> future;  // @GuardedBy("this")
 
     /**
      * Creates a new instance of {@code BackgroundInitializer}. No external
diff --git a/src/main/java/org/apache/commons/lang3/concurrent/TimedSemaphore.java b/src/main/java/org/apache/commons/lang3/concurrent/TimedSemaphore.java
index 1f27ae2bd..30043d6b8 100644
--- a/src/main/java/org/apache/commons/lang3/concurrent/TimedSemaphore.java
+++ b/src/main/java/org/apache/commons/lang3/concurrent/TimedSemaphore.java
@@ -149,28 +149,28 @@ public class TimedSemaphore {
     private final boolean ownExecutor;
 
     /** A future object representing the timer task. */
-    private ScheduledFuture<?> task;
+    private ScheduledFuture<?> task; // @GuardedBy("this")
 
     /** Stores the total number of invocations of the acquire() method. */
-    private long totalAcquireCount;
+    private long totalAcquireCount; // @GuardedBy("this")
 
     /**
      * The counter for the periods. This counter is increased every time a
      * period ends.
      */
-    private long periodCount;
+    private long periodCount; // @GuardedBy("this")
 
     /** The limit. */
-    private int limit;
+    private int limit; // @GuardedBy("this")
 
     /** The current counter. */
-    private int acquireCount;
+    private int acquireCount;  // @GuardedBy("this")
 
     /** The number of invocations of acquire() in the last period. */
-    private int lastCallsPerPeriod;
+    private int lastCallsPerPeriod; // @GuardedBy("this")
 
     /** A flag whether shutdown() was called. */
-    private boolean shutdown;
+    private boolean shutdown;  // @GuardedBy("this")
 
     /**
      * Creates a new instance of {@link TimedSemaphore} and initializes it with