diff --git a/.eslintrc.js b/.eslintrc.js
index 8f88ba30a07bf..715c6eb96074a 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -116,13 +116,8 @@ module.exports = {
     'react-internal/no-cross-fork-types': [
       ERROR,
       {
-        old: [
-          'firstEffect',
-          'nextEffect',
-          // Disabled because it's also used by the Hook type.
-          // 'lastEffect',
-        ],
-        new: ['subtreeFlags'],
+        old: [],
+        new: [],
       },
     ],
   },
@@ -190,7 +185,7 @@ module.exports = {
     {
       files: [
         'packages/react-native-renderer/**/*.js',
-        'packages/react-transport-native-relay/**/*.js'
+        'packages/react-transport-native-relay/**/*.js',
       ],
       globals: {
         nativeFabricUIManager: true,
diff --git a/packages/react-reconciler/src/ReactFiber.new.js b/packages/react-reconciler/src/ReactFiber.new.js
index 0dcff2f776fb4..ccad1371d8f40 100644
--- a/packages/react-reconciler/src/ReactFiber.new.js
+++ b/packages/react-reconciler/src/ReactFiber.new.js
@@ -141,6 +141,10 @@ function FiberNode(
 
   // Effects
   this.flags = NoFlags;
+  this.nextEffect = null;
+
+  this.firstEffect = null;
+  this.lastEffect = null;
   this.subtreeFlags = NoFlags;
   this.deletions = null;
 
@@ -805,6 +809,9 @@ export function assignFiberPropertiesInDEV(
   target.dependencies = source.dependencies;
   target.mode = source.mode;
   target.flags = source.flags;
+  target.nextEffect = source.nextEffect;
+  target.firstEffect = source.firstEffect;
+  target.lastEffect = source.lastEffect;
   target.subtreeFlags = source.subtreeFlags;
   target.deletions = source.deletions;
   target.lanes = source.lanes;
diff --git a/packages/react-reconciler/src/ReactFiber.old.js b/packages/react-reconciler/src/ReactFiber.old.js
index 57c421e9076a5..56ef2f5a528ab 100644
--- a/packages/react-reconciler/src/ReactFiber.old.js
+++ b/packages/react-reconciler/src/ReactFiber.old.js
@@ -145,6 +145,8 @@ function FiberNode(
 
   this.firstEffect = null;
   this.lastEffect = null;
+  this.subtreeFlags = NoFlags;
+  this.deletions = null;
 
   this.lanes = NoLanes;
   this.childLanes = NoLanes;
@@ -284,6 +286,8 @@ export function createWorkInProgress(current: Fiber, pendingProps: any): Fiber {
     workInProgress.nextEffect = null;
     workInProgress.firstEffect = null;
     workInProgress.lastEffect = null;
+    workInProgress.subtreeFlags = NoFlags;
+    workInProgress.deletions = null;
 
     if (enableProfilerTimer) {
       // We intentionally reset, rather than copy, actualDuration & actualStartTime.
@@ -372,6 +376,7 @@ export function resetWorkInProgress(workInProgress: Fiber, renderLanes: Lanes) {
     workInProgress.lanes = renderLanes;
 
     workInProgress.child = null;
+    workInProgress.subtreeFlags = NoFlags;
     workInProgress.memoizedProps = null;
     workInProgress.memoizedState = null;
     workInProgress.updateQueue = null;
@@ -392,6 +397,8 @@ export function resetWorkInProgress(workInProgress: Fiber, renderLanes: Lanes) {
     workInProgress.lanes = current.lanes;
 
     workInProgress.child = current.child;
+    workInProgress.subtreeFlags = current.subtreeFlags;
+    workInProgress.deletions = null;
     workInProgress.memoizedProps = current.memoizedProps;
     workInProgress.memoizedState = current.memoizedState;
     workInProgress.updateQueue = current.updateQueue;
@@ -814,6 +821,8 @@ export function assignFiberPropertiesInDEV(
   target.nextEffect = source.nextEffect;
   target.firstEffect = source.firstEffect;
   target.lastEffect = source.lastEffect;
+  target.subtreeFlags = source.subtreeFlags;
+  target.deletions = source.deletions;
   target.lanes = source.lanes;
   target.childLanes = source.childLanes;
   target.alternate = source.alternate;