diff --git a/packages/react-reconciler/src/ReactFiberUnwindWork.js b/packages/react-reconciler/src/ReactFiberUnwindWork.js
index f8c0b050f04a5..68cd4988f7f99 100644
--- a/packages/react-reconciler/src/ReactFiberUnwindWork.js
+++ b/packages/react-reconciler/src/ReactFiberUnwindWork.js
@@ -214,8 +214,9 @@ function throwException(
         // attach another listener to flip the boundary back to its normal state.
         const thenables: Set<Thenable> = (workInProgress.updateQueue: any);
         if (thenables === null) {
-          workInProgress.updateQueue = (new Set(): any);
-          workInProgress.updateQueue.add(thenable);
+          const updateQueue = (new Set(): any);
+          updateQueue.add(thenable);
+          workInProgress.updateQueue = updateQueue;
         } else {
           thenables.add(thenable);
         }