diff --git a/src/compiler/irgen.js b/src/compiler/irgen.js
index c3679fb41a7..880aaa82eaf 100644
--- a/src/compiler/irgen.js
+++ b/src/compiler/irgen.js
@@ -663,7 +663,7 @@ class ScriptTreeGenerator {
                 const blockInfo = this.getBlockInfo(block.opcode);
                 if (blockInfo) {
                     const type = blockInfo.info.blockType;
-                    if (type === BlockType.REPORTER || type === BlockType.BOOLEAN) {
+                    if (type === BlockType.REPORTER || type === BlockType.BOOLEAN || type === BlockType.INLINE) {
                         return this.descendCompatLayer(block);
                     }
                 }
@@ -1415,7 +1415,7 @@ class ScriptTreeGenerator {
         const blockInfo = this.getBlockInfo(block.opcode);
         const blockType = (blockInfo && blockInfo.info && blockInfo.info.blockType) || BlockType.COMMAND;
         const substacks = {};
-        if (blockType === BlockType.CONDITIONAL || blockType === BlockType.LOOP) {
+        if (blockType === BlockType.CONDITIONAL || blockType === BlockType.LOOP || blockType === BlockType.INLINE) {
             for (const inputName in block.inputs) {
                 if (!inputName.startsWith('SUBSTACK')) continue;
                 const branchNum = inputName === 'SUBSTACK' ? 1 : +inputName.substring('SUBSTACK'.length);
diff --git a/src/engine/runtime.js b/src/engine/runtime.js
index 6fc794268f7..448bf8e1ea1 100644
--- a/src/engine/runtime.js
+++ b/src/engine/runtime.js
@@ -1414,6 +1414,11 @@ class Runtime extends EventEmitter {
                 blockJSON.nextStatement = null; // null = available connection; undefined = terminal
             }
             break;
+        case BlockType.INLINE:
+            blockInfo.branchCount = blockInfo.branchCount || 1;
+            blockJSON.output = blockInfo.allowDropAnywhere ? null : 'String'; // TODO: distinguish number & string here?
+            blockJSON.outputShape = ScratchBlocksConstants.OUTPUT_SHAPE_SQUARE;
+            break;
         }
 
         const blockText = Array.isArray(blockInfo.text) ? blockInfo.text : [blockInfo.text];
diff --git a/src/extension-support/block-type.js b/src/extension-support/block-type.js
index ecaf70754dc..4680ef4af10 100644
--- a/src/extension-support/block-type.js
+++ b/src/extension-support/block-type.js
@@ -54,7 +54,13 @@ const BlockType = {
     /**
      * Arbitrary scratch-blocks XML.
      */
-    XML: 'xml'
+    XML: 'xml',
+
+    /**
+     * Specialized reporter block that allows for the insertion and evaluation
+     * of a substack.
+     */
+    INLINE: 'inline'
 };
 
 module.exports = BlockType;