diff -ru gtk-smooth-engine-0.6.0.1.orig//engines/shared/gtk/smooth_gtk_drawing.c gtk-smooth-engine-0.6.0.1/engines/shared/gtk/smooth_gtk_drawing.c
--- gtk-smooth-engine-0.6.0.1.orig//engines/shared/gtk/smooth_gtk_drawing.c	2010-08-27 20:27:50.000000000 -0400
+++ gtk-smooth-engine-0.6.0.1/engines/shared/gtk/smooth_gtk_drawing.c	2010-08-27 20:28:46.000000000 -0400
@@ -610,7 +610,7 @@
 		else
 			SmoothDrawBorderWithGap(&border, Canvas, base, x, y-thick, width, height+thick, GTK_POS_TOP, 0, width);
 	}
-	else if (CHECK_DETAIL(detail, "trough"))
+	else if (part && CHECK_DETAIL(detail, "trough"))
 	{
 			SmoothDrawBorderWithGap(&border, Canvas, base, x+PART_XPADDING(part), y+PART_YPADDING(part), 
 						width-PART_XPADDING(part)*2, height-PART_YPADDING(part)*2, 0, 0, 0);