diff --git a/src/table.cpp b/src/table.cpp
index 3da6831..c2c3636 100644
--- a/src/table.cpp
+++ b/src/table.cpp
@@ -144,7 +144,9 @@ void Table::setParentTableSet(TableSetBase *parent)
 {
     Q_D(Table);
     d->parentTableSet = parent;
-    d->parentTableSet->add(this);
+
+    if (parent)
+        d->parentTableSet->add(this);
 }
 
 TableSetBase *Table::childTableSet(const QString &name) const
diff --git a/src/tablesetbase.cpp b/src/tablesetbase.cpp
index 604fd0a..210819b 100644
--- a/src/tablesetbase.cpp
+++ b/src/tablesetbase.cpp
@@ -37,6 +37,12 @@ TableSetBase::TableSetBase(Table *parent) : QObject(parent),
     parent->add(this);
 }
 
+TableSetBase::~TableSetBase()
+{
+    foreach (Table *t, _tables)
+        t->setParentTableSet(nullptr);
+}
+
 int TableSetBase::save(Database *db, bool cleanUp)
 {
     int rowsAffected = 0;
diff --git a/src/tablesetbase_p.h b/src/tablesetbase_p.h
index 4967bbb..2a92abf 100644
--- a/src/tablesetbase_p.h
+++ b/src/tablesetbase_p.h
@@ -37,6 +37,7 @@ class TableSetBase : public QObject
 public:
     explicit TableSetBase(Database *parent);
     explicit TableSetBase(Table *parent);
+    virtual ~TableSetBase();
 
     virtual int save(Database *db, bool cleanUp = false);
     void clearChilds();