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,