diff --git a/src/test/kotlin/info/mking/k2zpl/command/GraphicBoxTest.kt b/src/test/kotlin/info/mking/k2zpl/command/GraphicBoxTest.kt
index 3f0672f..12bf788 100644
--- a/src/test/kotlin/info/mking/k2zpl/command/GraphicBoxTest.kt
+++ b/src/test/kotlin/info/mking/k2zpl/command/GraphicBoxTest.kt
@@ -59,6 +59,7 @@ class GraphicBoxTest : DescribeSpec({
                 row(1, 32001, 1, 1),
                 row(1, 1, 0, 1),
                 row(1, 1, 32001, 1),
+                row(1, 1, 1, -1),
                 row(1, 1, 1, 9)
             ).forAll { width, height, thickness, rounding ->
                 shouldThrow<IllegalArgumentException> {