diff --git a/services/core/java/com/android/server/Watchdog.java b/services/core/java/com/android/server/Watchdog.java
index a7fb99f8b004e..e097d85293ab3 100644
--- a/services/core/java/com/android/server/Watchdog.java
+++ b/services/core/java/com/android/server/Watchdog.java
@@ -617,9 +617,13 @@ public class Watchdog extends Thread {
             // deadlock and the watchdog as a whole to be ineffective)
             Thread dropboxThread = new Thread("watchdogWriteToDropbox") {
                     public void run() {
-                        mActivity.addErrorToDropBox(
-                                "watchdog", null, "system_server", null, null, null,
-                                subject, null, stack, null);
+                        // If a watched thread hangs before init() is called, we don't have a
+                        // valid mActivity. So we can't log the error to dropbox.
+                        if (mActivity != null) {
+                            mActivity.addErrorToDropBox(
+                                    "watchdog", null, "system_server", null, null, null,
+                                    subject, null, stack, null);
+                        }
                         StatsLog.write(StatsLog.SYSTEM_SERVER_WATCHDOG_OCCURRED, subject);
                     }
                 };