diff --git a/cwriter/writer_posix.go b/cwriter/writer_posix.go
index a32336f..f896c7b 100644
--- a/cwriter/writer_posix.go
+++ b/cwriter/writer_posix.go
@@ -7,6 +7,7 @@
 )
 
 // Flush flushes the underlying buffer.
+// It's caller's responsibility to pass correct number of lines.
 func (w *Writer) Flush(lines int) error {
 	_, err := w.WriteTo(w.out)
 	// some terminals interpret 'cursor up 0' as 'cursor up 1'
diff --git a/cwriter/writer_windows.go b/cwriter/writer_windows.go
index eebd027..77b67c6 100644
--- a/cwriter/writer_windows.go
+++ b/cwriter/writer_windows.go
@@ -16,6 +16,7 @@
 )
 
 // Flush flushes the underlying buffer.
+// It's caller's responsibility to pass correct number of lines.
 func (w *Writer) Flush(lines int) error {
 	if w.lines > 0 {
 		err := w.clearLines(w.lines)