diff --git a/include/mainwindow.h b/include/mainwindow.h
index 9113e227..27fe541c 100644
--- a/include/mainwindow.h
+++ b/include/mainwindow.h
@@ -216,6 +216,7 @@ private:
     bool openRecentProject();
     void updateTilesetEditor();
     QString getEventGroupFromTabWidget(QWidget *tab);
+    void closeSupplementaryWindows();
 
     bool isProjectOpen();
 };
diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index 595f4606..a0fcd6d0 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -293,6 +293,7 @@ bool MainWindow::openProject(QString dir) {
     projectConfig.setProjectDir(dir);
     projectConfig.load();
 
+    this->closeSupplementaryWindows();
     this->setProjectSpecificUIVisibility();
 
     bool already_open = isProjectOpen() && (editor->project->root == dir);
@@ -2410,6 +2411,17 @@ void MainWindow::on_actionRegion_Map_Editor_triggered() {
     }
 }
 
+void MainWindow::closeSupplementaryWindows() {
+    if (this->tilesetEditor)
+        delete this->tilesetEditor;
+    if (this->regionMapEditor)
+        delete this->regionMapEditor;
+    if (this->mapImageExporter)
+        delete this->mapImageExporter;
+    if (this->newmapprompt)
+        delete this->newmapprompt;
+}
+
 void MainWindow::closeEvent(QCloseEvent *event) {
     if (projectHasUnsavedChanges || editor->map->hasUnsavedChanges()) {
         QMessageBox::StandardButton result = QMessageBox::question(