diff --git a/System/Libraries/Graphics2D.HC b/System/Libraries/Graphics2D.HC
index 260d934..4c432c3 100644
--- a/System/Libraries/Graphics2D.HC
+++ b/System/Libraries/Graphics2D.HC
@@ -726,7 +726,7 @@ U0 VLine2D(Context2D* ctx, I64 x, I64 y, I64 y2,
 U0 HLine2D(Context2D* ctx, I64 x, I64 y, I64 x2,
     U32 color)
 { // Draw a horizontal line.
-    if (!ctx || !ctx->fb || x > ctx->width || y > ctx->height)
+    if (!ctx || !ctx->fb || x > ctx->width || y < 0 || y > ctx->height)
         return;
     if (x2 < x)
         return;