diff --git a/libs/canvas/framed_curve.cc b/libs/canvas/framed_curve.cc
index e8dee85c68..017d6528a0 100644
--- a/libs/canvas/framed_curve.cc
+++ b/libs/canvas/framed_curve.cc
@@ -193,7 +193,7 @@ FramedCurve::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) c
 			left = idx;
 		}
 
-		for (Points::size_type idx = n_samples; idx > left + 1; --idx) {
+		for (Points::size_type idx = n_samples - 1; idx > left + 1; --idx) {
 			window_space = item_to_window (Duple (samples[idx].x, 0.0));
 			if (window_space.x <= draw.x1) break;
 			right = idx;