diff --git a/bigtext.py b/bigtext.py
index e324c5a..8c7c69c 100644
--- a/bigtext.py
+++ b/bigtext.py
@@ -257,9 +257,9 @@ class InnerBigText(QWidget):
             # print("-> %s,%s" %(self._selection_start_byte, self._selection_end_byte))
         line_number = self.y_pos_to_line(e.pos().y())
         column_in_line = self.x_pos_to_column(e.pos().x())
-        if line_number == 0:
+        if line_number < 0:
             self.scroll_by_lines(-1)
-        if line_number + 1 >= int(self.lines_shown()):
+        if line_number > int(self.lines_shown()):
             self.scroll_by_lines(1)
         if column_in_line <= 1:
             self._left_offset = max(0, self._left_offset - 2)