diff --git a/internal/stroke/stroke.go b/internal/stroke/stroke.go
index 4073e422..6a6b3877 100644
--- a/internal/stroke/stroke.go
+++ b/internal/stroke/stroke.go
@@ -327,6 +327,9 @@ func strokePathNorm(p0, p1, p2 f32.Point, t, d float32) f32.Point {
 func rot90CW(p f32.Point) f32.Point { return f32.Pt(+p.Y, -p.X) }
 
 func normPt(p f32.Point, l float32) f32.Point {
+	if p.X == 0 && p.Y == 0 {
+		return f32.Point{}
+	}
 	isVerticalUnit := p.X == 0 && (p.Y == l || p.Y == -l)
 	isHorizontalUnit := p.Y == 0 && (p.X == l || p.X == -l)
 	if isVerticalUnit || isHorizontalUnit {
diff --git a/internal/stroke/stroke_test.go b/internal/stroke/stroke_test.go
index 80f2296e..8e6630bd 100644
--- a/internal/stroke/stroke_test.go
+++ b/internal/stroke/stroke_test.go
@@ -16,6 +16,10 @@ func TestNormPt(t *testing.T) {
 	}
 
 	scenarios := []scenario{
+		// l!=0 && X=Y=0
+		{l: 10, ptIn: f32.Point{X: 0, Y: 0}, ptOut: f32.Point{X: 0, Y: 0}},
+		{l: -10, ptIn: f32.Point{X: 0, Y: 0}, ptOut: f32.Point{X: 0, Y: 0}},
+
 		// l>0 & X
 		{l: +20, ptIn: f32.Point{X: +30, Y: 0}, ptOut: f32.Point{X: +20, Y: 0}},
 		{l: +20, ptIn: f32.Point{X: +20, Y: 0}, ptOut: f32.Point{X: +20, Y: 0}},