diff --git a/packages/react-reconciler/src/ReactInternalTypes.js b/packages/react-reconciler/src/ReactInternalTypes.js
index d643b1f9c2612..0227970a77b33 100644
--- a/packages/react-reconciler/src/ReactInternalTypes.js
+++ b/packages/react-reconciler/src/ReactInternalTypes.js
@@ -157,12 +157,6 @@ export type Fiber = {
   subtreeFlags: Flags,
   deletions: Array<Fiber> | null,
 
-  // The first and last fiber with side-effect within this subtree. This allows
-  // us to reuse a slice of the linked list when we reuse the work done within
-  // this fiber.
-  firstEffect: Fiber | null,
-  lastEffect: Fiber | null,
-
   lanes: Lanes,
   childLanes: Lanes,