diff --git a/core/scrollbar.js b/core/scrollbar.js
index e872900f00..624ae270ae 100644
--- a/core/scrollbar.js
+++ b/core/scrollbar.js
@@ -243,7 +243,7 @@ Blockly.Scrollbar.prototype.resize = function(opt_metrics) {
       // Only show the scrollbar if needed.
       // Ideally this would also apply to scrollbar pairs, but that's a bigger
       // headache (due to interactions with the corner square).
-      this.setVisible(outerLength < hostMetrics.contentHeight);
+      this.setVisible(outerLength < hostMetrics.contentWidth);
     }
     this.ratio_ = outerLength / hostMetrics.contentWidth;
     if (this.ratio_ === -Infinity || this.ratio_ === Infinity ||