diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.js b/packages/react-reconciler/src/ReactFiberBeginWork.js
index fb71d18581..9e8077b7a2 100644
--- a/packages/react-reconciler/src/ReactFiberBeginWork.js
+++ b/packages/react-reconciler/src/ReactFiberBeginWork.js
@@ -146,7 +146,11 @@ export function reconcileChildren(
   }
 }
 
-function updateForwardRef(current, workInProgress, renderExpirationTime) {
+function updateForwardRef(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderExpirationTime: ExpirationTime,
+) {
   const render = workInProgress.type.render;
   const nextProps = workInProgress.pendingProps;
   const ref = workInProgress.ref;
@@ -184,7 +188,11 @@ function updateForwardRef(current, workInProgress, renderExpirationTime) {
   return workInProgress.child;
 }
 
-function updateFragment(current, workInProgress, renderExpirationTime) {
+function updateFragment(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderExpirationTime: ExpirationTime,
+) {
   const nextChildren = workInProgress.pendingProps;
   reconcileChildren(
     current,
@@ -196,7 +204,11 @@ function updateFragment(current, workInProgress, renderExpirationTime) {
   return workInProgress.child;
 }
 
-function updateMode(current, workInProgress, renderExpirationTime) {
+function updateMode(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderExpirationTime: ExpirationTime,
+) {
   const nextChildren = workInProgress.pendingProps.children;
   reconcileChildren(
     current,
@@ -208,7 +220,11 @@ function updateMode(current, workInProgress, renderExpirationTime) {
   return workInProgress.child;
 }
 
-function updateProfiler(current, workInProgress, renderExpirationTime) {
+function updateProfiler(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderExpirationTime: ExpirationTime,
+) {
   if (enableProfilerTimer) {
     workInProgress.effectTag |= Update;
   }
@@ -768,7 +784,11 @@ function updatePlaceholderComponent(
   }
 }
 
-function updatePortalComponent(current, workInProgress, renderExpirationTime) {
+function updatePortalComponent(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderExpirationTime: ExpirationTime,
+) {
   pushHostContainer(workInProgress, workInProgress.stateNode.containerInfo);
   const nextChildren = workInProgress.pendingProps;
   if (current === null) {
@@ -796,7 +816,11 @@ function updatePortalComponent(current, workInProgress, renderExpirationTime) {
   return workInProgress.child;
 }
 
-function updateContextProvider(current, workInProgress, renderExpirationTime) {
+function updateContextProvider(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderExpirationTime: ExpirationTime,
+) {
   const providerType: ReactProviderType<any> = workInProgress.type;
   const context: ReactContext<any> = providerType._context;
 
@@ -859,7 +883,11 @@ function updateContextProvider(current, workInProgress, renderExpirationTime) {
   return workInProgress.child;
 }
 
-function updateContextConsumer(current, workInProgress, renderExpirationTime) {
+function updateContextConsumer(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderExpirationTime: ExpirationTime,
+) {
   const context: ReactContext<any> = workInProgress.type;
   const newProps = workInProgress.pendingProps;
   const render = newProps.children;