diff --git a/services/java/com/android/server/WindowManagerService.java b/services/java/com/android/server/WindowManagerService.java
index 00636c400ae52..20b01d2d745a7 100644
--- a/services/java/com/android/server/WindowManagerService.java
+++ b/services/java/com/android/server/WindowManagerService.java
@@ -3971,7 +3971,9 @@ public class WindowManagerService extends IWindowManager.Stub
             != PackageManager.PERMISSION_GRANTED) {
             throw new SecurityException("Requires DISABLE_KEYGUARD permission");
         }
-        mKeyguardDisabled.acquire(token, tag);
+        synchronized (mKeyguardDisabled) {
+            mKeyguardDisabled.acquire(token, tag);
+        }
     }
 
     public void reenableKeyguard(IBinder token) {