diff --git a/oqtopus/gui/database_connection_widget.py b/oqtopus/gui/database_connection_widget.py
index a88f8b6..af354a7 100644
--- a/oqtopus/gui/database_connection_widget.py
+++ b/oqtopus/gui/database_connection_widget.py
@@ -53,6 +53,10 @@ def __init__(self, parent=None):
             # Silence errors during widget initialization
             pass
 
+    def close(self):
+        """Close the database connection."""
+        self.__set_connection(None)
+
     def getConnection(self):
         """
         Returns the current database connection.
diff --git a/oqtopus/gui/main_dialog.py b/oqtopus/gui/main_dialog.py
index 737e562..96d47c3 100644
--- a/oqtopus/gui/main_dialog.py
+++ b/oqtopus/gui/main_dialog.py
@@ -152,6 +152,7 @@ def closeEvent(self, event):
             )
             event.ignore()
             return
+        self.__databaseConnectionWidget.close()
         self.__moduleWidget.close()
         self.__moduleSelectionWidget.close()
         self.__logsWidget.close()
@@ -165,6 +166,7 @@ def __closeDialog(self):
                 self.tr("Cannot close the dialog while an operation is running."),
             )
             return
+        self.__databaseConnectionWidget.close()
         self.__moduleWidget.close()
         self.__moduleSelectionWidget.close()
         self.__logsWidget.close()