diff --git a/core/block.js b/core/block.js
index a6bea0c58..a3d794a8c 100644
--- a/core/block.js
+++ b/core/block.js
@@ -226,6 +226,13 @@ Blockly.Block.obtain = function(workspace, prototypeName) {
  */
 Blockly.Block.prototype.data = null;
 
+/**
+ * Has this block been disposed of?
+ * @type {boolean}
+ * @package
+ */
+Blockly.Block.prototype.disposed = false;
+
 /**
  * Colour of the block as HSV hue value (0-360)
  * This may be null if the block colour was not set via a hue number.
diff --git a/core/connection.js b/core/connection.js
index d727f97c8..7594642a2 100644
--- a/core/connection.js
+++ b/core/connection.js
@@ -71,6 +71,13 @@ Blockly.Connection.REASON_SHADOW_PARENT = 6;
  */
 Blockly.Connection.prototype.targetConnection = null;
 
+/**
+ * Has this connection been disposed of?
+ * @type {boolean}
+ * @package
+ */
+Blockly.Connection.prototype.disposed = false;
+
 /**
  * List of compatible value types.  Null if all types are compatible.
  * @type {Array}
diff --git a/core/field.js b/core/field.js
index 09bb1f1df..51bde7c69 100644
--- a/core/field.js
+++ b/core/field.js
@@ -149,6 +149,7 @@ Blockly.Field.X_PADDING = 10;
  * @type {[type]}
  */
 Blockly.Field.DEFAULT_TEXT_OFFSET = Blockly.Field.X_PADDING / 2;
+
 /**
  * Name of field.  Unique within each block.
  * Static labels are usually unnamed.
@@ -156,6 +157,13 @@ Blockly.Field.DEFAULT_TEXT_OFFSET = Blockly.Field.X_PADDING / 2;
  */
 Blockly.Field.prototype.name = undefined;
 
+/**
+ * Has this field been disposed of?
+ * @type {boolean}
+ * @package
+ */
+Blockly.Field.prototype.disposed = false;
+
 /**
  * Maximum characters of text to display before adding an ellipsis.
  * @type {number}
diff --git a/tests/mocha/block_test.js b/tests/mocha/block_test.js
index f22560a83..b0d87ed4f 100644
--- a/tests/mocha/block_test.js
+++ b/tests/mocha/block_test.js
@@ -190,7 +190,7 @@ suite('Blocks', function() {
     });
     suite('Dispose', function() {
       function assertDisposedNoheal(blocks) {
-        chai.assert.isNotOk(blocks.A.disposed);
+        chai.assert.isFalse(blocks.A.disposed);
         // A has nothing connected to it.
         chai.assert.equal(0, blocks.A.getChildren().length);
         // B is disposed.
@@ -199,8 +199,8 @@ suite('Blocks', function() {
         chai.assert.isTrue(blocks.C.disposed);
       }
       function assertDisposedHealed(blocks) {
-        chai.assert.isNotOk(blocks.A.disposed);
-        chai.assert.isNotOk(blocks.C.disposed);
+        chai.assert.isFalse(blocks.A.disposed);
+        chai.assert.isFalse(blocks.C.disposed);
         // A and C are connected.
         assertEquals(1, blocks.A.getChildren().length);
         assertEquals(blocks.A, blocks.C.getParent());
@@ -371,7 +371,7 @@ suite('Blocks', function() {
               .connect(blockB.outputConnection);
 
           this.blockA.removeInput('VALUE');
-          chai.assert.isNotOk(blockB.disposed);
+          chai.assert.isFalse(blockB.disposed);
           chai.assert.equal(this.blockA.getChildren().length, 0);
         });
         test('Shadow Connected', function() {
@@ -400,7 +400,7 @@ suite('Blocks', function() {
               .connect(blockB.previousConnection);
 
           this.blockA.removeInput('STATEMENT');
-          chai.assert.isNotOk(blockB.disposed);
+          chai.assert.isFalse(blockB.disposed);
           chai.assert.equal(this.blockA.getChildren().length, 0);
         });
         test('Shadow Connected', function() {
diff --git a/tests/mocha/connection_test.js b/tests/mocha/connection_test.js
index 0e8884160..9f7f726c6 100644
--- a/tests/mocha/connection_test.js
+++ b/tests/mocha/connection_test.js
@@ -20,7 +20,6 @@
 
 suite('Connections', function() {
 
-
   suite.skip('Rendered', function() {
     function assertAllConnectionsHiddenState(block, hidden) {
       var connections = block.getConnections_(true);