diff --git a/lib/reline/line_editor.rb b/lib/reline/line_editor.rb
index c6d0c9f698..f93731d722 100644
--- a/lib/reline/line_editor.rb
+++ b/lib/reline/line_editor.rb
@@ -592,14 +592,14 @@ def add_dialog_proc(name, p, context = nil)
     if diff > 0
       dialog.column -= diff
     end
-    if (lower_space + @rest_height) >= DIALOG_HEIGHT
+    if (lower_space + @rest_height - pos.y) >= DIALOG_HEIGHT
       dialog.vertical_offset = pos.y + 1
     elsif upper_space >= DIALOG_HEIGHT
       dialog.vertical_offset = pos.y + -(DIALOG_HEIGHT + 1)
     else
-      if (lower_space + @rest_height) < DIALOG_HEIGHT
-        scroll_down(DIALOG_HEIGHT)
-        move_cursor_up(DIALOG_HEIGHT)
+      if (lower_space + @rest_height - pos.y) < DIALOG_HEIGHT
+        scroll_down(DIALOG_HEIGHT + pos.y)
+        move_cursor_up(DIALOG_HEIGHT + pos.y)
       end
       dialog.vertical_offset = pos.y + 1
     end