diff --git a/app/src/main/java/io/heckel/ntfy/msg/ApiService.kt b/app/src/main/java/io/heckel/ntfy/msg/ApiService.kt
index 1152f0a..2bea4c1 100644
--- a/app/src/main/java/io/heckel/ntfy/msg/ApiService.kt
+++ b/app/src/main/java/io/heckel/ntfy/msg/ApiService.kt
@@ -157,6 +157,9 @@ class ApiService {
 
     companion object {
         private const val TAG = "NtfyApiService"
+
+        // These constants have corresponding values in the server codebase!
+        const val CONTROL_TOPIC = "~control"
         const val EVENT_MESSAGE = "message"
         const val EVENT_KEEPALIVE = "keepalive"
     }
diff --git a/app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt b/app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt
index 22def38..a1b9a9e 100644
--- a/app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt
+++ b/app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt
@@ -117,7 +117,7 @@ class MainActivity : AppCompatActivity(), ActionMode.Callback, AddFragment.Subsc
         notifier!!.createNotificationChannels()
 
         // Subscribe to control Firebase channel (so we can re-start the foreground service if it dies)
-        messenger.subscribe("~keepalive")
+        messenger.subscribe(ApiService.CONTROL_TOPIC)
 
         // Background things
         startPeriodicPollWorker()