diff --git a/rtdata/themes/RawTherapee-GTK3-20_.css b/rtdata/themes/RawTherapee-GTK3-20_.css
index a5f52a769..bdadc00db 100644
--- a/rtdata/themes/RawTherapee-GTK3-20_.css
+++ b/rtdata/themes/RawTherapee-GTK3-20_.css
@@ -565,7 +565,7 @@ button.text-button.toggle:hover:checked {
 .drawingarea {
     border-radius: 0;
     background-color: #2A2A2A;
-    border: 0.0833333333333333em solid #1D1D1D;
+    border: 0.0833333333333333em solid #888888;
 }
 .drawingarea:disabled {
     background-color: #444;
diff --git a/rtgui/mydiagonalcurve.cc b/rtgui/mydiagonalcurve.cc
index ac7976b7e..ce6c6f3ec 100644
--- a/rtgui/mydiagonalcurve.cc
+++ b/rtgui/mydiagonalcurve.cc
@@ -323,7 +323,7 @@ void MyDiagonalCurve::draw (int handle)
     // draw the grid lines:
     cr->set_line_width (1.0 * s);
     c = style->get_border_color(state);
-    cr->set_source_rgb (c.get_red(), c.get_green(), c.get_blue());
+    cr->set_source_rgba (c.get_red(), c.get_green(), c.get_blue(), 0.3);
     cr->set_antialias (Cairo::ANTIALIAS_NONE);
 
     for (int i = 0; i <= 10; i++) {