diff -r 2fccf75e8b5f javafx-ui-charts/src/javafx/scene/chart/XYChart.java
--- a/javafx-ui-charts/src/javafx/scene/chart/XYChart.java	Mon Aug 22 13:39:31 2011 -0700
+++ b/javafx-ui-charts/src/javafx/scene/chart/XYChart.java	Tue Aug 23 11:45:33 2011 -0700
@@ -632,7 +632,7 @@
             verticalZeroLine.setEndY(top+yAxisHeight);
             verticalZeroLine.setVisible(true);
         }
-        if(Double.isNaN(xAxisZero) || !isHorizontalZeroLineVisible()) {
+        if(Double.isNaN(yAxisZero) || !isHorizontalZeroLineVisible()) {
             horizontalZeroLine.setVisible(false);
         } else {
             horizontalZeroLine.setStartX(left);