diff --git a/blocks_vertical/vertical_extensions.js b/blocks_vertical/vertical_extensions.js
index 96e2684534..47c3f06a90 100644
--- a/blocks_vertical/vertical_extensions.js
+++ b/blocks_vertical/vertical_extensions.js
@@ -232,6 +232,10 @@ Blockly.ScratchBlocks.VerticalExtensions.SCRATCH_EXTENSION = function() {
   this.isScratchExtension = true;
 };
 
+Blockly.ScratchBlocks.VerticalExtensions.SHADOW_ARGUMENT_REPORTER = function() {
+  this.shadow_argument_reporter = true;
+};
+
 /**
  * Register all extensions for scratch-blocks.
  * @package
@@ -284,6 +288,10 @@ Blockly.ScratchBlocks.VerticalExtensions.registerAll = function() {
   // Misleading name. Given to blocks that have an extension icon.
   Blockly.Extensions.register('scratch_extension',
       Blockly.ScratchBlocks.VerticalExtensions.SCRATCH_EXTENSION);
+  
+  // Blocks that are regenerative shadow reporters
+  Blockly.Extensions.register('shadow_argument_reporter',
+      Blockly.ScratchBlocks.VerticalExtensions.SHADOW_ARGUMENT_REPORTER);
 };
 
 Blockly.ScratchBlocks.VerticalExtensions.registerAll();
diff --git a/core/block.js b/core/block.js
index ae49a86015..38f4020322 100644
--- a/core/block.js
+++ b/core/block.js
@@ -210,6 +210,12 @@ Blockly.Block = function(workspace, prototypeName, opt_id) {
   }
 };
 
+/**
+ * Whether or not this block is a shadow argument reporter. (used by VM)
+ * @type {boolean}
+ */
+Blockly.Block.prototype.shadow_argument_reporter = false;
+
 /**
  * Optional text data that round-trips beween blocks and XML.
  * Has no effect. May be used by 3rd parties for meta information.
diff --git a/core/scratch_blocks_utils.js b/core/scratch_blocks_utils.js
index aa44203c5d..90de26be25 100644
--- a/core/scratch_blocks_utils.js
+++ b/core/scratch_blocks_utils.js
@@ -72,6 +72,17 @@ Blockly.scratchBlocksUtils.changeObscuredShadowIds = function(block) {
   }
 };
 
+/**
+ * Set of blocks that have special behaviour in scratch-blocks where they're
+ * duplicated when dragged, and they are rendered slightly differently from
+ * normalshadow blocks.
+ * @type {string[]}
+ */
+Blockly.scratchBlocksUtils.shadowArgumentReporters = [
+  'argument_reporter_boolean',
+  'argument_reporter_string_number'
+];
+
 /**
  * Whether a block is both a shadow block and an argument reporter.  These
  * blocks have special behaviour in scratch-blocks: they're duplicated when
@@ -83,8 +94,10 @@ Blockly.scratchBlocksUtils.changeObscuredShadowIds = function(block) {
  * @package
  */
 Blockly.scratchBlocksUtils.isShadowArgumentReporter = function(block) {
-  return (block.isShadow() && (block.type == 'argument_reporter_boolean' ||
-      block.type == 'argument_reporter_string_number'));
+  return (block.isShadow() && (
+    Blockly.scratchBlocksUtils.shadowArgumentReporters.includes(block.type) ||
+    block.shadow_argument_reporter
+  ));
 };
 
 /**