diff --git a/packages/react-devtools-shared/src/backend/renderer.js b/packages/react-devtools-shared/src/backend/renderer.js
index 5e09a2d0f804..055b57ee4b52 100644
--- a/packages/react-devtools-shared/src/backend/renderer.js
+++ b/packages/react-devtools-shared/src/backend/renderer.js
@@ -2630,6 +2630,10 @@ export function attach(
   }
 
   function handleCommitFiberUnmount(fiber) {
+    // Flush any pending Fibers that we are untracking before processing the new commit.
+    // If we don't do this, we might end up double-deleting Fibers in some cases (like Legacy Suspense).
+    untrackFibers();
+
     // This is not recursive.
     // We can't traverse fibers after unmounting so instead
     // we rely on React telling us about each unmount.