diff --git a/core/block_svg.js b/core/block_svg.js
index 4745b8d32..7fc41293d 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -956,9 +956,16 @@ Blockly.BlockSvg.prototype.onMouseMove_ = function(e) {
       Blockly.dragMode_ = Blockly.DRAG_FREE;
       Blockly.longStop_();
       this.workspace.setResizesEnabled(false);
-      if (this.parentBlock_) {
-        // Push this block to the very top of the stack.
-        this.unplug();
+
+      var disconnectEffect = !!this.parentBlock_;
+      // If in a stack, either split the stack, or pull out single block.
+      var healStack = !Blockly.DRAG_STACK;
+      if (e.altKey || e.ctrlKey || e.metaKey) {
+        healStack = !healStack;
+      }
+      // Push this block to the very top of the stack.
+      this.unplug(healStack);
+      if (disconnectEffect) {
         var group = this.getSvgRoot();
         group.translate_ = 'translate(' + newXY.x + ',' + newXY.y + ')';
         this.disconnectUiEffect();
diff --git a/core/constants.js b/core/constants.js
index d3fac8a62..f69531ee7 100644
--- a/core/constants.js
+++ b/core/constants.js
@@ -54,10 +54,16 @@ Blockly.LONGPRESS = 750;
 
 /**
  * Prevent a sound from playing if another sound preceded it within this many
- * miliseconds.
+ * milliseconds.
  */
 Blockly.SOUND_LIMIT = 100;
 
+/**
+ * When dragging a block out of a stack, split the stack in two (true), or drag
+ * out the block healing the stack (false).
+ */
+Blockly.DRAG_STACK = true;
+
 /**
  * The richness of block colours, regardless of the hue.
  * Must be in the range of 0 (inclusive) to 1 (exclusive).