diff --git a/core/interfaces/i_positionable.js b/core/interfaces/i_positionable.js
index 89f4c8094..356510c81 100644
--- a/core/interfaces/i_positionable.js
+++ b/core/interfaces/i_positionable.js
@@ -37,6 +37,7 @@ Blockly.IPositionable.prototype.position;
 /**
  * Returns the bounding rectangle of the UI element in pixel units relative to
  * the Blockly injection div.
- * @return {!Blockly.utils.Rect} The UI elements’s bounding box.
+ * @return {?Blockly.utils.Rect} The UI elements’s bounding box. Null if
+ *   bounding box should be ignored by other UI elements.
  */
 Blockly.IPositionable.prototype.getBoundingRectangle;
diff --git a/core/trashcan.js b/core/trashcan.js
index 968ee916c..f6ad48ba4 100644
--- a/core/trashcan.js
+++ b/core/trashcan.js
@@ -506,7 +506,8 @@ Blockly.Trashcan.prototype.position = function(metrics, savedPositions) {
 /**
  * Returns the bounding rectangle of the UI element in pixel units relative to
  * the Blockly injection div.
- * @return {!Blockly.utils.Rect} The UI elements’s bounding box.
+ * @return {?Blockly.utils.Rect} The UI elements’s bounding box. Null if
+ *   bounding box should be ignored by other UI elements.
  */
 Blockly.Trashcan.prototype.getBoundingRectangle = function() {
   var bottom = this.top_ + this.BODY_HEIGHT_ + this.LID_HEIGHT_;
diff --git a/core/workspace_svg.js b/core/workspace_svg.js
index ea06193bc..95618dbef 100644
--- a/core/workspace_svg.js
+++ b/core/workspace_svg.js
@@ -1148,7 +1148,10 @@ Blockly.WorkspaceSvg.prototype.resize = function() {
   var savedPositions = [];
   for (var i = 0, positionable; (positionable = positionables[i]); i++) {
     positionable.position(metrics, savedPositions);
-    savedPositions.push(positionable.getBoundingRectangle());
+    var boundingRect = positionable.getBoundingRectangle();
+    if (boundingRect) {
+      savedPositions.push(boundingRect);
+    }
   }
 
   if (this.scrollbar) {
diff --git a/core/zoom_controls.js b/core/zoom_controls.js
index b86111a3b..07c63e904 100644
--- a/core/zoom_controls.js
+++ b/core/zoom_controls.js
@@ -228,7 +228,8 @@ Blockly.ZoomControls.prototype.dispose = function() {
 /**
  * Returns the bounding rectangle of the UI element in pixel units relative to
  * the Blockly injection div.
- * @return {!Blockly.utils.Rect} The UI elements’s bounding box.
+ * @return {?Blockly.utils.Rect} The UI elements’s bounding box. Null if
+ *   bounding box should be ignored by other UI elements.
  */
 Blockly.ZoomControls.prototype.getBoundingRectangle = function() {
   var height = this.SMALL_SPACING_ + 2 * this.HEIGHT_;