diff --git a/src/terminal.go b/src/terminal.go
index 9cc1fdac..bb1a8ff4 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -1717,6 +1717,12 @@ func (t *Terminal) separatedByBorder() bool {
 	if t.inputBorderShape.Visible() {
 		return true
 	}
+	if t.previewOpts.position == posNext {
+		// A preview window at 'next' position sits right next to the input
+		// section instead. Keep the separator, as the visibility and the
+		// border of the preview window can change at runtime.
+		return false
+	}
 	hasHeaderLinesWindow, headerLinesShape := t.determineHeaderLinesShape()
 	hasHeaderWindow := t.hasHeaderWindow()
 	if !hasHeaderWindow && !hasHeaderLinesWindow {