diff --git a/src/gui_qt/io/asciireader.py b/src/gui_qt/io/asciireader.py
index 7bf5a06..4a41bc0 100644
--- a/src/gui_qt/io/asciireader.py
+++ b/src/gui_qt/io/asciireader.py
@@ -113,7 +113,7 @@ class QAsciiReader(QtWidgets.QDialog, Ui_ascii_reader):
     @QtCore.pyqtSlot(int, name='on_line_spinBox_valueChanged')
     def set_column_names(self, _):
         self.ascii_table.setHorizontalHeaderLabels(map(str, range(1, self.ascii_table.columnCount() + 1)))
-        if self.column_checkBox.isChecked():
+        if self.column_checkBox.isChecked() and self.line_spinBox.isEnabled():
             header_line = self.reader.header[self.line_spinBox.value()-1]
             self.ascii_table.setHorizontalHeaderLabels(header_line.split())