diff --git a/core/block.js b/core/block.js
index b5229edc5..cfeaddebd 100644
--- a/core/block.js
+++ b/core/block.js
@@ -742,25 +742,33 @@ Blockly.Block.prototype.getChildren = function(ordered) {
  * @package
  */
 Blockly.Block.prototype.setParent = function(newParent) {
-  if (newParent == this.parentBlock_) {
+  if (newParent === this.parentBlock_) {
     return;
   }
+
+  // Check that block is connected to new parent if new parent is not null and
+  //    that block is not connected to superior one if new parent is null.
+  var connection = this.previousConnection || this.outputConnection;
+  var isConnected = !!(connection && connection.targetBlock());
+
+  if (isConnected && newParent && connection.targetBlock() !== newParent) {
+    throw Error('Block connected to superior one that is not new parent.');
+  } else if (!isConnected && newParent) {
+    throw Error('Block not connected to new parent.');
+  } else if (isConnected && !newParent) {
+    throw Error('Cannot set parent to null while block is still connected to' +
+        ' superior block.');
+  }
+
   if (this.parentBlock_) {
     // Remove this block from the old parent's child list.
     Blockly.utils.arrayRemove(this.parentBlock_.childBlocks_, this);
 
-    // Disconnect from superior blocks.
-    if (this.previousConnection && this.previousConnection.isConnected()) {
-      throw Error('Still connected to previous block.');
-    }
-    if (this.outputConnection && this.outputConnection.isConnected()) {
-      throw Error('Still connected to parent block.');
-    }
-    this.parentBlock_ = null;
     // This block hasn't actually moved on-screen, so there's no need to update
-    // its connection locations.
+    //     its connection locations.
   } else {
-    // Remove this block from the workspace's list of top-most blocks.
+    // New parent must be non-null so remove this block from the workspace's
+    //     list of top-most blocks.
     this.workspace.removeTopBlock(this);
   }
 
diff --git a/tests/mocha/block_test.js b/tests/mocha/block_test.js
index cf602a386..7c841a134 100644
--- a/tests/mocha/block_test.js
+++ b/tests/mocha/block_test.js
@@ -890,6 +890,96 @@ suite('Blocks', function() {
         chai.assert.equal(this.getNext().length, 6);
       });
     });
+    suite('Setting Parent Block', function() {
+      setup(function() {
+        this.printBlock = Blockly.Xml.domToBlock(Blockly.Xml.textToDom(
+            '<block type="text_print">' +
+            '  <value name="TEXT">' +
+            '    <block type="text_join">' +
+            '      <mutation items="2"></mutation>' +
+            '      <value name="ADD0">' +
+            '        <block type="text">' +
+            '        </block>' +
+            '      </value>' +
+            '    </block>' +
+            '  </value>' +
+            '</block>'
+        ), this.workspace);
+        this.textJoinBlock = this.printBlock.getInputTargetBlock('TEXT');
+        this.textBlock = this.textJoinBlock.getInputTargetBlock('ADD0');
+      });
+
+      function assertBlockIsOnlyChild(parent, child, inputName) {
+        chai.assert.equal(parent.getChildren().length, 1);
+        chai.assert.equal(parent.getInputTargetBlock(inputName), child);
+        chai.assert.equal(child.getParent(), parent);
+      }
+      function assertNonParentAndOrphan(nonParent, orphan, inputName) {
+        chai.assert.equal(nonParent.getChildren().length, 0);
+        chai.assert.isNull(nonParent.getInputTargetBlock('TEXT'));
+        chai.assert.isNull(orphan.getParent());
+      }
+      function assertOriginalSetup() {
+        assertBlockIsOnlyChild(this.printBlock, this.textJoinBlock, 'TEXT');
+        assertBlockIsOnlyChild(this.textJoinBlock, this.textBlock, 'ADD0');
+      }
+
+      test('Setting to connected parent', function() {
+        chai.assert.doesNotThrow(this.textJoinBlock.setParent
+            .bind(this.textJoinBlock, this.printBlock));
+        assertOriginalSetup.call(this);
+      });
+      test('Setting to new parent after connecting to it', function() {
+        this.textJoinBlock.outputConnection.disconnect();
+        this.textBlock.outputConnection
+            .connect(this.printBlock.getInput('TEXT').connection);
+        chai.assert.doesNotThrow(this.textBlock.setParent
+            .bind(this.textBlock, this.printBlock));
+        assertBlockIsOnlyChild(this.printBlock, this.textBlock, 'TEXT');
+      });
+      test('Setting to new parent while connected to other block', function() {
+        // Setting to grandparent with no available input connection.
+        chai.assert.throws(this.textBlock.setParent
+            .bind(this.textBlock, this.printBlock));
+        this.textJoinBlock.outputConnection.disconnect();
+        // Setting to block with available input connection.
+        chai.assert.throws(this.textBlock.setParent
+            .bind(this.textBlock, this.printBlock));
+        assertNonParentAndOrphan(this.printBlock, this.textJoinBlock, 'TEXT');
+        assertBlockIsOnlyChild(this.textJoinBlock, this.textBlock, 'ADD0');
+      });
+      test('Setting to same parent after disconnecting from it', function() {
+        this.textJoinBlock.outputConnection.disconnect();
+        chai.assert.throws(this.textJoinBlock.setParent
+            .bind(this.textJoinBlock, this.printBlock));
+        assertNonParentAndOrphan(this.printBlock, this.textJoinBlock, 'TEXT');
+      });
+      test('Setting to new parent when orphan', function() {
+        this.textBlock.outputConnection.disconnect();
+        // When new parent has no available input connection.
+        chai.assert.throws(this.textBlock.setParent
+            .bind(this.textBlock, this.printBlock));
+        this.textJoinBlock.outputConnection.disconnect();
+        // When new parent has available input connection.
+        chai.assert.throws(this.textBlock.setParent
+            .bind(this.textBlock, this.printBlock));
+
+        assertNonParentAndOrphan(this.printBlock, this.textJoinBlock, 'TEXT');
+        assertNonParentAndOrphan(this.printBlock, this.textBlock, 'TEXT');
+        assertNonParentAndOrphan(this.textJoinBlock, this.textBlock, 'ADD0');
+      });
+      test('Setting parent to null after disconnecting', function() {
+        this.textBlock.outputConnection.disconnect();
+        chai.assert.doesNotThrow(this.textBlock.setParent
+            .bind(this.textBlock, null));
+        assertNonParentAndOrphan(this.textJoinBlock, this.textBlock, 'ADD0');
+      });
+      test('Setting parent to null without disconnecting', function() {
+        chai.assert.throws(this.textBlock.setParent
+            .bind(this.textBlock, null));
+        assertOriginalSetup.call(this);
+      });
+    });
     suite('Remove Connections Programmatically', function() {
       test('Output', function() {
         var block = createRenderedBlock(this.workspace, 'row_block');
@@ -1106,11 +1196,16 @@ suite('Blocks', function() {
   });
   suite('Getting/Setting Field (Values)', function() {
     setup(function() {
+      this.workspace = Blockly.inject('blocklyDiv');
       this.block = Blockly.Xml.domToBlock(Blockly.Xml.textToDom(
           '<block type="text"><field name = "TEXT">test</field></block>'
       ), this.workspace);
     });
 
+    teardown(function() {
+      workspaceTeardown.call(this, this.workspace);
+    });
+
     test('Getting Field', function() {
       chai.assert.instanceOf(this.block.getField('TEXT'), Blockly.Field);
     });