diff --git a/compat/java/android/support/v4/provider/SelfDestructiveThread.java b/compat/java/android/support/v4/provider/SelfDestructiveThread.java
index 90fa723..258f522 100644
--- a/compat/java/android/support/v4/provider/SelfDestructiveThread.java
+++ b/compat/java/android/support/v4/provider/SelfDestructiveThread.java
@@ -40,7 +40,7 @@
  */
 @RestrictTo(LIBRARY_GROUP)
 public class SelfDestructiveThread {
-    private Object mLock = new Object();
+    private final Object mLock = new Object();
 
     @GuardedBy("mLock")
     private HandlerThread mThread;