From e4edc3899a497feecd9eabd18e04b817b6d25125 Mon Sep 17 00:00:00 2001
From: marisaleung <marisaleung@google.com>
Date: Tue, 11 Apr 2017 15:33:51 -0700
Subject: [PATCH] Ensure useDragSurface is a boolean.

Fixed #988
---
 core/block_svg.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/block_svg.js b/core/block_svg.js
index 418804083..aebded139 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -89,7 +89,7 @@ Blockly.BlockSvg = function(workspace, prototypeName, opt_id) {
    * @type {boolean}
    * @private
    */
-  this.useDragSurface_ = Blockly.utils.is3dSupported() && workspace.blockDragSurface_;
+  this.useDragSurface_ = Blockly.utils.is3dSupported() && !!workspace.blockDragSurface_;
 
   Blockly.Tooltip.bindMouseEvents(this.svgPath_);
   Blockly.BlockSvg.superClass_.constructor.call(this,