JavaFX 8 -> 11 ComboBox Regression

FXTestCB.java

import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.application.Application;
import javafx.scene.control.*;
import javafx.scene.layout.VBox;
import javafx.scene.input.KeyCode;
import javafx.geometry.Insets;

public class FXTestCB extends Application {
	public static void main (String[] args) { launch(args); }
	
	public void start(Stage stage) {	
		
		VBox root = new VBox();
		ComboBox<String> cb = new ComboBox<>();
		cb.setPromptText("Sample"); 
		cb.getItems().addAll("Jane", "Mary", "Doe");
		Button btn = new Button ("OK");
		
		cb.setOnKeyPressed(kp -> 
			{
				if (kp.getCode().equals(KeyCode.F5)) {
					cb.getSelectionModel().clearSelection();
					//cb.getItems().clear();
					btn.requestFocus();
				}
			}
		);
		btn.setOnAction( ae -> cb.getItems().addAll("Jane", "Mary", "Doe") );
		
		root.getChildren().addAll(cb, btn);
		stage.setScene( new Scene (root, 100, 100) );
		stage.show();
	}
}

Clearing the selected item AND clearing the items list, individually, both cause the prompt text to disappear in JavaFX 11. This is not the case in JavaFX 8.