diff --git a/src/core/db/databasereader.cpp b/src/core/db/databasereader.cpp
index 1616e8c90..0262f1a11 100644
--- a/src/core/db/databasereader.cpp
+++ b/src/core/db/databasereader.cpp
@@ -45,6 +45,7 @@ namespace swift::core::db
     void CDatabaseReader::readInBackgroundThread(CEntityFlags::Entity entities, const QDateTime &newerThan)
     {
         if (!this->doWorkCheck()) { return; }
+        Q_ASSERT_X(hasStarted(), Q_FUNC_INFO, "Thread was not started yet!");
 
         // we accept cached data
         Q_ASSERT_X(!entities.testFlag(CEntityFlags::DbInfoObjectEntity), Q_FUNC_INFO, "Read info objects directly");
diff --git a/src/core/threadedreaderperiodic.cpp b/src/core/threadedreaderperiodic.cpp
index 0c4bf3f0f..3e802123f 100644
--- a/src/core/threadedreaderperiodic.cpp
+++ b/src/core/threadedreaderperiodic.cpp
@@ -13,6 +13,7 @@ namespace swift::core
 
     void CThreadedReaderPeriodic::startReader()
     {
+        Q_ASSERT_X(hasStarted(), Q_FUNC_INFO, "Thread was not started yet!");
         Q_ASSERT(m_initialTime > 0);
         QTimer::singleShot(m_initialTime, this, [=] { this->doWork(); });
     }
diff --git a/src/core/vatsim/vatsimserverfilereader.cpp b/src/core/vatsim/vatsimserverfilereader.cpp
index 79da6be0d..a187d9bf5 100644
--- a/src/core/vatsim/vatsimserverfilereader.cpp
+++ b/src/core/vatsim/vatsimserverfilereader.cpp
@@ -36,6 +36,7 @@ namespace swift::core::vatsim
 
     void CVatsimServerFileReader::readInBackgroundThread()
     {
+        Q_ASSERT_X(hasStarted(), Q_FUNC_INFO, "Thread was not started yet!");
         QPointer<CVatsimServerFileReader> myself(this);
         QTimer::singleShot(0, this, [=] {
             if (!myself) { return; }
diff --git a/src/core/vatsim/vatsimstatusfilereader.cpp b/src/core/vatsim/vatsimstatusfilereader.cpp
index 9def3b3d9..54b221fc8 100644
--- a/src/core/vatsim/vatsimstatusfilereader.cpp
+++ b/src/core/vatsim/vatsimstatusfilereader.cpp
@@ -38,6 +38,7 @@ namespace swift::core::vatsim
 
     void CVatsimStatusFileReader::readInBackgroundThread()
     {
+        Q_ASSERT_X(hasStarted(), Q_FUNC_INFO, "Thread was not started yet!");
         QPointer<CVatsimStatusFileReader> myself(this);
         QTimer::singleShot(0, this, [=] {
             if (!myself) { return; }