diff --git a/flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatOptionPaneTest.java b/flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatOptionPaneTest.java
index 9eb2f325..ef4bd234 100644
--- a/flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatOptionPaneTest.java
+++ b/flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatOptionPaneTest.java
@@ -21,6 +21,7 @@ import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
 import javax.swing.*;
 import javax.swing.border.*;
+import com.formdev.flatlaf.FlatClientProperties;
 import com.formdev.flatlaf.demo.ScrollablePanel;
 import net.miginfocom.swing.*;
 
@@ -63,6 +64,15 @@ public class FlatOptionPaneTest
 		UIManager.put( "OptionPane.showIcon", showTitleBarIconCheckBox.isSelected() );
 	}
 
+	private void showWithCustomIcon() {
+		JOptionPane optionPane = new JOptionPane( "Hello world." );
+		JDialog dialog = optionPane.createDialog( "With Custom Icon" );
+		dialog.getRootPane().putClientProperty( FlatClientProperties.TITLE_BAR_SHOW_ICON, true );
+		dialog.setIconImage( new ImageIcon( FlatOptionPaneTest.class.getResource( "/com/formdev/flatlaf/testing/test32.png" ) ).getImage() );
+		dialog.setVisible( true );
+		dialog.dispose();
+	}
+
 	private void initComponents() {
 		// JFormDesigner - Component initialization - DO NOT MODIFY  //GEN-BEGIN:initComponents
 		ScrollablePanel panel9 = new ScrollablePanel();
@@ -75,6 +85,7 @@ public class FlatOptionPaneTest
 		JPanel panel2 = new JPanel();
 		JOptionPane errorOptionPane = new JOptionPane();
 		errorShowDialogLabel = new FlatOptionPaneTest.ShowDialogLinkLabel();
+		JButton showWithCustomIconButton = new JButton();
 		JLabel informationLabel = new JLabel();
 		JPanel panel3 = new JPanel();
 		JOptionPane informationOptionPane = new JOptionPane();
@@ -173,6 +184,11 @@ public class FlatOptionPaneTest
 			errorShowDialogLabel.setOptionPane(errorOptionPane);
 			panel9.add(errorShowDialogLabel, "cell 1 1");
 
+			//---- showWithCustomIconButton ----
+			showWithCustomIconButton.setText("Show with custom icon");
+			showWithCustomIconButton.addActionListener(e -> showWithCustomIcon());
+			panel9.add(showWithCustomIconButton, "cell 2 1");
+
 			//---- informationLabel ----
 			informationLabel.setText("Information");
 			panel9.add(informationLabel, "cell 0 2");
diff --git a/flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatOptionPaneTest.jfd b/flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatOptionPaneTest.jfd
index 26deae19..87e72473 100644
--- a/flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatOptionPaneTest.jfd
+++ b/flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatOptionPaneTest.jfd
@@ -1,4 +1,4 @@
-JFDML JFormDesigner: "7.0.4.0.360" Java: "16" encoding: "UTF-8"
+JFDML JFormDesigner: "8.2.3.0.386" Java: "21" encoding: "UTF-8"
 
 new FormModel {
 	contentType: "form/swing"
@@ -83,6 +83,13 @@ new FormModel {
 				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 					"value": "cell 1 1"
 				} )
+				add( new FormComponent( "javax.swing.JButton" ) {
+					name: "showWithCustomIconButton"
+					"text": "Show with custom icon"
+					addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "showWithCustomIcon", false ) )
+				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+					"value": "cell 2 1"
+				} )
 				add( new FormComponent( "javax.swing.JLabel" ) {
 					name: "informationLabel"
 					"text": "Information"