diff --git a/flatlaf-core/src/main/java/com/formdev/flatlaf/UIDefaultsLoader.java b/flatlaf-core/src/main/java/com/formdev/flatlaf/UIDefaultsLoader.java
index 26a5a6b7..da3557d5 100644
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/UIDefaultsLoader.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/UIDefaultsLoader.java
@@ -332,16 +332,17 @@ class UIDefaultsLoader
 
 	private static Object parseBorder( String value, Function<String, String> resolver, List<ClassLoader> addonClassLoaders ) {
 		if( value.indexOf( ',' ) >= 0 ) {
-			// top,left,bottom,right[,lineColor]
+			// top,left,bottom,right[,lineColor[,lineThickness]]
 			List<String> parts = split( value, ',' );
 			Insets insets = parseInsets( value );
-			ColorUIResource lineColor = (parts.size() == 5)
+			ColorUIResource lineColor = (parts.size() >= 5)
 				? (ColorUIResource) parseColorOrFunction( resolver.apply( parts.get( 4 ) ), resolver, true )
 				: null;
+			float lineThickness = (parts.size() >= 6) ? parseFloat( parts.get( 5 ), true ) : 1f;
 
 			return (LazyValue) t -> {
 				return (lineColor != null)
-					? new FlatLineBorder( insets, lineColor )
+					? new FlatLineBorder( insets, lineColor, lineThickness )
 					: new FlatEmptyBorder( insets );
 			};
 		} else
diff --git a/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatLineBorder.java b/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatLineBorder.java
index 355bf01d..5af4c531 100644
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatLineBorder.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatLineBorder.java
@@ -26,9 +26,9 @@ import java.awt.Insets;
 /**
  * Line border for various components.
  *
- * Paints a scaled 1px thick line around the component.
- * The line thickness is not included in the border insets.
- * The insets should be at least 1,1,1,1.
+ * Paints a scaled (usually 1px thick) line around the component.
+ * The line thickness is not added to the border insets.
+ * The insets should be at least have line thickness (usually 1,1,1,1).
  *
  * @author Karl Tauber
  */
@@ -36,10 +36,16 @@ public class FlatLineBorder
 	extends FlatEmptyBorder
 {
 	private final Color lineColor;
+	private final float lineThickness;
 
 	public FlatLineBorder( Insets insets, Color lineColor ) {
+		this( insets, lineColor, 1f );
+	}
+
+	public FlatLineBorder( Insets insets, Color lineColor, float lineThickness ) {
 		super( insets );
 		this.lineColor = lineColor;
+		this.lineThickness = lineThickness;
 	}
 
 	@Override
@@ -48,7 +54,7 @@ public class FlatLineBorder
 		try {
 			FlatUIUtils.setRenderingHints( g2 );
 			g2.setColor( lineColor );
-			FlatUIUtils.paintComponentBorder( g2, x, y, width, height, 0f, scale( 1f ), 0f );
+			FlatUIUtils.paintComponentBorder( g2, x, y, width, height, 0f, scale( lineThickness ), 0f );
 		} finally {
 			g2.dispose();
 		}