diff --git a/packages/SystemUI/src/com/android/systemui/keyguard/Lifecycle.java b/packages/SystemUI/src/com/android/systemui/keyguard/Lifecycle.java
index 1b20cfbc4e550..3da6caf319689 100644
--- a/packages/SystemUI/src/com/android/systemui/keyguard/Lifecycle.java
+++ b/packages/SystemUI/src/com/android/systemui/keyguard/Lifecycle.java
@@ -16,7 +16,10 @@
 
 package com.android.systemui.keyguard;
 
+import androidx.annotation.NonNull;
+
 import java.util.ArrayList;
+import java.util.Objects;
 import java.util.function.Consumer;
 
 /**
@@ -26,8 +29,8 @@ public class Lifecycle<T> {
 
     private ArrayList<T> mObservers = new ArrayList<>();
 
-    public void addObserver(T observer) {
-        mObservers.add(observer);
+    public void addObserver(@NonNull T observer) {
+        mObservers.add(Objects.requireNonNull(observer));
     }
 
     public void removeObserver(T observer) {
diff --git a/packages/SystemUI/tests/src/com/android/systemui/keyguard/WakefulnessLifecycleTest.java b/packages/SystemUI/tests/src/com/android/systemui/keyguard/WakefulnessLifecycleTest.java
index 1dc415048f74b..2e8e3ed664b34 100644
--- a/packages/SystemUI/tests/src/com/android/systemui/keyguard/WakefulnessLifecycleTest.java
+++ b/packages/SystemUI/tests/src/com/android/systemui/keyguard/WakefulnessLifecycleTest.java
@@ -122,4 +122,8 @@ public class WakefulnessLifecycleTest extends SysuiTestCase {
         mWakefulness.dump(null, new PrintWriter(new ByteArrayOutputStream()), new String[0]);
     }
 
-}
\ No newline at end of file
+    @Test(expected = NullPointerException.class)
+    public void throwNPEOnNullObserver() {
+        mWakefulness.addObserver(null);
+    }
+}