diff --git a/src/lib/blocks.js b/src/lib/blocks.js
index 97d5ec30dea..3230729c8ad 100644
--- a/src/lib/blocks.js
+++ b/src/lib/blocks.js
@@ -328,7 +328,7 @@ export default function (vm, useCatBlocks) {
         this.jsonInit(json);
     };
 
-    ScratchBlocks.VerticalFlyout.getCheckboxState = function (blockId) {
+    ScratchBlocks.CheckableContinuousFlyout.prototype.getCheckboxState = function (blockId) {
         const monitoredBlock = vm.runtime.monitorBlocks._blocks[blockId];
         return monitoredBlock ? monitoredBlock.isMonitored : false;
     };