diff --git a/shader_test.go b/shader_test.go
index 13ebf8c28..9e8dcdb80 100644
--- a/shader_test.go
+++ b/shader_test.go
@@ -84,6 +84,79 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 	}
 }
 
+func TestShaderFillWithDrawTriangles(t *testing.T) {
+	const w, h = 16, 16
+
+	dst, _ := NewImage(w, h, FilterDefault)
+	s, err := NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	return vec4(1, 0, 0, 1)
+}
+`))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	src, _ := NewImage(w/2, h/2, FilterDefault)
+	op := &DrawTrianglesOptions{}
+	op.Shader = s
+	vs := []Vertex{
+		{
+			DstX:   0,
+			DstY:   0,
+			SrcX:   0,
+			SrcY:   0,
+			ColorR: 1,
+			ColorG: 1,
+			ColorB: 1,
+			ColorA: 1,
+		},
+		{
+			DstX:   w,
+			DstY:   0,
+			SrcX:   w / 2,
+			SrcY:   0,
+			ColorR: 1,
+			ColorG: 1,
+			ColorB: 1,
+			ColorA: 1,
+		},
+		{
+			DstX:   0,
+			DstY:   h,
+			SrcX:   0,
+			SrcY:   h / 2,
+			ColorR: 1,
+			ColorG: 1,
+			ColorB: 1,
+			ColorA: 1,
+		},
+		{
+			DstX:   w,
+			DstY:   h,
+			SrcX:   w / 2,
+			SrcY:   h / 2,
+			ColorR: 1,
+			ColorG: 1,
+			ColorB: 1,
+			ColorA: 1,
+		},
+	}
+	is := []uint16{0, 1, 2, 1, 2, 3}
+	dst.DrawTriangles(vs, is, src, op)
+
+	for j := 0; j < h; j++ {
+		for i := 0; i < w; i++ {
+			got := dst.At(i, j).(color.RGBA)
+			want := color.RGBA{0xff, 0, 0, 0xff}
+			if got != want {
+				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
+			}
+		}
+	}
+}
+
 func TestShaderFunction(t *testing.T) {
 	const w, h = 16, 16