diff --git a/app/src/main/java/eu/faircode/email/Core.java b/app/src/main/java/eu/faircode/email/Core.java
index 0d800ceccd..9bc3766778 100644
--- a/app/src/main/java/eu/faircode/email/Core.java
+++ b/app/src/main/java/eu/faircode/email/Core.java
@@ -2392,6 +2392,7 @@ class Core {
         private Semaphore semaphore = new Semaphore(0);
         private boolean running = true;
         private boolean recoverable = true;
+        List<State> childs = Collections.synchronizedList(new ArrayList<>());
 
         State(ConnectionHelper.NetworkState networkState) {
             this.networkState = networkState;
diff --git a/app/src/main/java/eu/faircode/email/ServiceSynchronize.java b/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
index e502354d78..e798903cef 100644
--- a/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
+++ b/app/src/main/java/eu/faircode/email/ServiceSynchronize.java
@@ -506,7 +506,6 @@ public class ServiceSynchronize extends ServiceBase {
             private PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
             private PowerManager.WakeLock wl = pm.newWakeLock(
                     PowerManager.PARTIAL_WAKE_LOCK, BuildConfig.APPLICATION_ID + ":main");
-            private List<Core.State> threadState = new ArrayList<>();
 
             @Override
             public void run() {
@@ -549,7 +548,7 @@ public class ServiceSynchronize extends ServiceBase {
                             }
                         }, "sync.account." + account.id);
                         astate.start();
-                        threadState.add(astate);
+                        state.childs.add(astate);
                     }
 
                     EntityLog.log(ServiceSynchronize.this, "Main started");
@@ -564,11 +563,11 @@ public class ServiceSynchronize extends ServiceBase {
                     }
 
                     // Stop monitoring accounts
-                    for (Core.State astate : threadState)
+                    for (Core.State astate : state.childs)
                         astate.stop();
-                    for (Core.State astate : threadState)
+                    for (Core.State astate : state.childs)
                         astate.join();
-                    threadState.clear();
+                    state.childs.clear();
 
                     EntityLog.log(ServiceSynchronize.this, "Main exited");
                 } catch (Throwable ex) {