diff --git a/packages/react-reconciler/src/ReactDebugAsyncWarnings.js b/packages/react-reconciler/src/ReactDebugAsyncWarnings.js
index 5aeb102d69718..0dbd802df95af 100644
--- a/packages/react-reconciler/src/ReactDebugAsyncWarnings.js
+++ b/packages/react-reconciler/src/ReactDebugAsyncWarnings.js
@@ -11,7 +11,7 @@ import type {Fiber} from './ReactFiber';
 
 import getComponentName from 'shared/getComponentName';
 import {getStackAddendumByWorkInProgressFiber} from 'shared/ReactFiberComponentTreeHook';
-import {AsyncUpdates} from './ReactTypeOfInternalContext';
+import {AsyncUpdates, PreAsyncUpdates} from './ReactTypeOfInternalContext';
 import warning from 'fbjs/lib/warning';
 
 type LIFECYCLE =
@@ -94,7 +94,10 @@ if (__DEV__) {
     let maybeAsyncRoot = null;
 
     while (fiber !== null) {
-      if (fiber.internalContextTag & AsyncUpdates) {
+      if (
+        fiber.internalContextTag & AsyncUpdates ||
+        fiber.internalContextTag & PreAsyncUpdates
+      ) {
         maybeAsyncRoot = fiber;
       }
 
diff --git a/packages/react-reconciler/src/ReactFiberClassComponent.js b/packages/react-reconciler/src/ReactFiberClassComponent.js
index 4eed41271806d..9a9bb5f978a66 100644
--- a/packages/react-reconciler/src/ReactFiberClassComponent.js
+++ b/packages/react-reconciler/src/ReactFiberClassComponent.js
@@ -26,7 +26,7 @@ import invariant from 'fbjs/lib/invariant';
 import warning from 'fbjs/lib/warning';
 
 import {startPhaseTimer, stopPhaseTimer} from './ReactDebugFiberPerf';
-import {AsyncUpdates} from './ReactTypeOfInternalContext';
+import {AsyncUpdates, PreAsyncUpdates} from './ReactTypeOfInternalContext';
 import {
   cacheContext,
   getMaskedContext,
@@ -637,16 +637,24 @@ export default function(
     if (
       enableAsyncSubtreeAPI &&
       workInProgress.type != null &&
-      workInProgress.type.prototype != null &&
-      workInProgress.type.prototype.unstable_isAsyncReactComponent === true
+      workInProgress.type.prototype != null
     ) {
-      workInProgress.internalContextTag |= AsyncUpdates;
+      const prototype = workInProgress.type.prototype;
+
+      if (prototype.unstable_isAsyncReactComponent === true) {
+        workInProgress.internalContextTag |= AsyncUpdates;
+      } else if (prototype.unstable_isPreAsyncReactComponent === true) {
+        workInProgress.internalContextTag |= PreAsyncUpdates;
+      }
     }
 
     if (__DEV__) {
       // If we're inside of an async sub-tree,
       // Warn about any unsafe lifecycles on this class component.
-      if (workInProgress.internalContextTag & AsyncUpdates) {
+      if (
+        workInProgress.internalContextTag & AsyncUpdates ||
+        workInProgress.internalContextTag & PreAsyncUpdates
+      ) {
         ReactDebugAsyncWarnings.recordLifecycleWarnings(
           workInProgress,
           instance,
diff --git a/packages/react-reconciler/src/ReactTypeOfInternalContext.js b/packages/react-reconciler/src/ReactTypeOfInternalContext.js
index 24859845f79f0..015c90cca2d63 100644
--- a/packages/react-reconciler/src/ReactTypeOfInternalContext.js
+++ b/packages/react-reconciler/src/ReactTypeOfInternalContext.js
@@ -9,5 +9,6 @@
 
 export type TypeOfInternalContext = number;
 
-export const NoContext = 0;
-export const AsyncUpdates = 1;
+export const NoContext = 0b00000000;
+export const AsyncUpdates = 0b00000001;
+export const PreAsyncUpdates = 0b00000010;
diff --git a/packages/react/src/React.js b/packages/react/src/React.js
index 61a59f83c530b..4a2081edbe86c 100644
--- a/packages/react/src/React.js
+++ b/packages/react/src/React.js
@@ -9,7 +9,12 @@ import assign from 'object-assign';
 import ReactVersion from 'shared/ReactVersion';
 import {REACT_FRAGMENT_TYPE} from 'shared/ReactSymbols';
 
-import {Component, PureComponent, AsyncComponent} from './ReactBaseClasses';
+import {
+  Component,
+  PureComponent,
+  AsyncComponent,
+  PreAsyncComponent,
+} from './ReactBaseClasses';
 import {forEach, map, count, toArray, only} from './ReactChildren';
 import ReactCurrentOwner from './ReactCurrentOwner';
 import {
@@ -37,6 +42,7 @@ const React = {
   Component,
   PureComponent,
   unstable_AsyncComponent: AsyncComponent,
+  unstable_PreAsyncComponent: PreAsyncComponent,
 
   Fragment: REACT_FRAGMENT_TYPE,
 
diff --git a/packages/react/src/ReactBaseClasses.js b/packages/react/src/ReactBaseClasses.js
index 13d4ab999bfba..b95d158041198 100644
--- a/packages/react/src/ReactBaseClasses.js
+++ b/packages/react/src/ReactBaseClasses.js
@@ -117,44 +117,56 @@ if (__DEV__) {
   }
 }
 
-/**
- * Base class helpers for the updating state of a component.
- */
+function ComponentDummy() {}
+ComponentDummy.prototype = Component.prototype;
+
+function configurePrototype(ComponentSubclass, prototypeProperties) {
+  const prototype = (ComponentSubclass.prototype = new ComponentDummy());
+  prototype.constructor = ComponentSubclass;
+
+  // Avoid an extra prototype jump for these methods.
+  Object.assign(prototype, Component.prototype);
+
+  // Mixin additional properties
+  Object.assign(prototype, prototypeProperties);
+}
+
+// Convenience component with default shallow equality check for sCU.
 function PureComponent(props, context, updater) {
-  // Duplicated from Component.
   this.props = props;
   this.context = context;
   this.refs = emptyObject;
-  // We initialize the default updater but the real one gets injected by the
-  // renderer.
   this.updater = updater || ReactNoopUpdateQueue;
 }
+configurePrototype(PureComponent, {isPureReactComponent: true});
 
-function ComponentDummy() {}
-ComponentDummy.prototype = Component.prototype;
-const pureComponentPrototype = (PureComponent.prototype = new ComponentDummy());
-pureComponentPrototype.constructor = PureComponent;
-// Avoid an extra prototype jump for these methods.
-Object.assign(pureComponentPrototype, Component.prototype);
-pureComponentPrototype.isPureReactComponent = true;
-
+// Special component type that opts subtree into async rendering mode.
 function AsyncComponent(props, context, updater) {
-  // Duplicated from Component.
   this.props = props;
   this.context = context;
   this.refs = emptyObject;
-  // We initialize the default updater but the real one gets injected by the
-  // renderer.
   this.updater = updater || ReactNoopUpdateQueue;
 }
+configurePrototype(AsyncComponent, {
+  unstable_isAsyncReactComponent: true,
+  render: function render() {
+    return this.props.children;
+  },
+});
 
-const asyncComponentPrototype = (AsyncComponent.prototype = new ComponentDummy());
-asyncComponentPrototype.constructor = AsyncComponent;
-// Avoid an extra prototype jump for these methods.
-Object.assign(asyncComponentPrototype, Component.prototype);
-asyncComponentPrototype.unstable_isAsyncReactComponent = true;
-asyncComponentPrototype.render = function() {
-  return this.props.children;
-};
+// Special component type that enables async rendering dev warnings.
+// This helps detect unsafe lifecycles without enabling actual async behavior.
+function PreAsyncComponent(props, context, updater) {
+  this.props = props;
+  this.context = context;
+  this.refs = emptyObject;
+  this.updater = updater || ReactNoopUpdateQueue;
+}
+configurePrototype(PreAsyncComponent, {
+  unstable_isPreAsyncReactComponent: true,
+  render: function render() {
+    return this.props.children;
+  },
+});
 
-export {Component, PureComponent, AsyncComponent};
+export {Component, PureComponent, AsyncComponent, PreAsyncComponent};
diff --git a/packages/react/src/__tests__/ReactAsyncClassComponent-test.internal.js b/packages/react/src/__tests__/ReactAsyncClassComponent-test.internal.js
index a559d401001ea..e8e6a51538133 100644
--- a/packages/react/src/__tests__/ReactAsyncClassComponent-test.internal.js
+++ b/packages/react/src/__tests__/ReactAsyncClassComponent-test.internal.js
@@ -419,5 +419,58 @@ describe('ReactAsyncClassComponent', () => {
 
       expect(caughtError).not.toBe(null);
     });
+
+    it('should also warn inside of pre-async trees', () => {
+      class SyncRoot extends React.Component {
+        UNSAFE_componentWillMount() {}
+        UNSAFE_componentWillUpdate() {}
+        UNSAFE_componentWillReceiveProps() {}
+        render() {
+          return <PreAsyncRoot />;
+        }
+      }
+      class PreAsyncRoot extends React.unstable_PreAsyncComponent {
+        UNSAFE_componentWillMount() {}
+        render() {
+          return <Wrapper />;
+        }
+      }
+      function Wrapper({children}) {
+        return (
+          <div>
+            <Bar />
+            <Foo />
+          </div>
+        );
+      }
+      class Foo extends React.Component {
+        UNSAFE_componentWillReceiveProps() {}
+        render() {
+          return null;
+        }
+      }
+      class Bar extends React.Component {
+        UNSAFE_componentWillReceiveProps() {}
+        render() {
+          return null;
+        }
+      }
+
+      expect(() => ReactTestRenderer.create(<SyncRoot />)).toWarnDev(
+        'Unsafe lifecycle methods were found within the following async tree:' +
+          '\n    in PreAsyncRoot (at **)' +
+          '\n    in SyncRoot (at **)' +
+          '\n\ncomponentWillMount: Please update the following components ' +
+          'to use componentDidMount instead: PreAsyncRoot' +
+          '\n\ncomponentWillReceiveProps: Please update the following components ' +
+          'to use static getDerivedStateFromProps instead: Bar, Foo' +
+          '\n\nLearn more about this warning here:' +
+          '\nhttps://fb.me/react-async-component-lifecycle-hooks',
+      );
+
+      // Dedupe
+      const rendered = ReactTestRenderer.create(<SyncRoot />);
+      rendered.update(<SyncRoot />);
+    });
   });
 });