diff --git a/src/lib/blocks.js b/src/lib/blocks.js
index 892218dbe..809a77ce2 100644
--- a/src/lib/blocks.js
+++ b/src/lib/blocks.js
@@ -213,6 +213,18 @@ export default function (vm) {
 
     ScratchBlocks.Blocks.sensing_of.init = function () {
         const blockId = this.id;
+        const blockType = this.type;
+
+        // Get the sensing_of block from vm.
+        let defaultSensingOfBlock;
+        const blocks = vm.runtime.flyoutBlocks._blocks;
+        Object.keys(blocks).forEach(id => {
+            const block = blocks[id];
+            if (id === blockType || (block && block.opcode === blockType)) {
+                defaultSensingOfBlock = block;
+            }
+        });
+
         // Function that fills in menu for the first input in the sensing block.
         // Called every time it opens since it depends on the values in the other block input.
         const menuFn = function () {
@@ -236,7 +248,7 @@ export default function (vm) {
 
                 // The block doesn't exist, but should be in the flyout. Look there.
                 if (!sensingOfBlock) {
-                    sensingOfBlock = vm.runtime.flyoutBlocks.getBlock(blockId);
+                    sensingOfBlock = vm.runtime.flyoutBlocks.getBlock(blockId) || defaultSensingOfBlock;
                     // If we still don't have a block, just return an empty list . This happens during
                     // scratch blocks construction.
                     if (!sensingOfBlock) {