diff --git a/src/isomorphic/classic/element/ReactDebugCurrentFrame.js b/src/isomorphic/classic/element/ReactDebugCurrentFrame.js
index f4efdd672b..9cfbab11c4 100644
--- a/src/isomorphic/classic/element/ReactDebugCurrentFrame.js
+++ b/src/isomorphic/classic/element/ReactDebugCurrentFrame.js
@@ -18,12 +18,7 @@ import type { DebugID } from 'ReactInstanceType';
 const ReactDebugCurrentFrame = {};
 
 if (__DEV__) {
-  var {
-    getStackAddendumByID,
-    getStackAddendumByWorkInProgressFiber,
-    getCurrentStackAddendum,
-  } = require('ReactComponentTreeHook');
-
+  var ReactComponentTreeHook = require('ReactComponentTreeHook');
   // Component that is being worked on
   ReactDebugCurrentFrame.current = (null : Fiber | DebugID | null);
 
@@ -38,16 +33,16 @@ if (__DEV__) {
       if (typeof current === 'number') {
         // DebugID from Stack.
         const debugID = current;
-        stack = getStackAddendumByID(debugID);
+        stack = (ReactComponentTreeHook: any).getStackAddendumByID(debugID);
       } else if (typeof current.tag === 'number') {
         // This is a Fiber.
         // The stack will only be correct if this is a work in progress
         // version and we're calling it during reconciliation.
         const workInProgress = current;
-        stack = getStackAddendumByWorkInProgressFiber(workInProgress);
+        stack = ReactComponentTreeHook.getStackAddendumByWorkInProgressFiber(workInProgress);
       }
     } else if (element !== null) {
-      stack = getCurrentStackAddendum(element);
+      stack = (ReactComponentTreeHook: any).getCurrentStackAddendum(element);
     }
     return stack;
   };
diff --git a/src/isomorphic/hooks/ReactComponentTreeHook.js b/src/isomorphic/hooks/ReactComponentTreeHook.js
index 2359fd1c34..40c9a50279 100644
--- a/src/isomorphic/hooks/ReactComponentTreeHook.js
+++ b/src/isomorphic/hooks/ReactComponentTreeHook.js
@@ -12,7 +12,11 @@
 
 'use strict';
 
-var ReactCurrentOwner = require('ReactCurrentOwner');
+import type { ReactElement, Source } from 'ReactElementType';
+import type { DebugID } from 'ReactInstanceType';
+import type { Fiber } from 'ReactFiber';
+
+var getComponentName = require('getComponentName');
 var ReactTypeOfWork = require('ReactTypeOfWork');
 var {
   IndeterminateComponent,
@@ -21,144 +25,6 @@ var {
   HostComponent,
 } = ReactTypeOfWork;
 
-var getComponentName = require('getComponentName');
-var invariant = require('fbjs/lib/invariant');
-var warning = require('fbjs/lib/warning');
-
-import type { ReactElement, Source } from 'ReactElementType';
-import type { DebugID } from 'ReactInstanceType';
-import type { Fiber } from 'ReactFiber';
-
-function isNative(fn) {
-  // Based on isNative() from Lodash
-  var funcToString = Function.prototype.toString;
-  var hasOwnProperty = Object.prototype.hasOwnProperty;
-  var reIsNative = RegExp('^' + funcToString
-    // Take an example native function source for comparison
-    .call(hasOwnProperty)
-    // Strip regex characters so we can use it for regex
-    .replace(/[\\^$.*+?()[\]{}|]/g, '\\$&')
-    // Remove hasOwnProperty from the template to make it generic
-    .replace(
-      /hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g,
-      '$1.*?'
-    ) + '$'
-  );
-  try {
-    var source = funcToString.call(fn);
-    return reIsNative.test(source);
-  } catch (err) {
-    return false;
-  }
-}
-
-var canUseCollections = (
-  // Array.from
-  typeof Array.from === 'function' &&
-  // Map
-  typeof Map === 'function' &&
-  isNative(Map) &&
-  // Map.prototype.keys
-  Map.prototype != null &&
-  typeof Map.prototype.keys === 'function' &&
-  isNative(Map.prototype.keys) &&
-  // Set
-  typeof Set === 'function' &&
-  isNative(Set) &&
-  // Set.prototype.keys
-  Set.prototype != null &&
-  typeof Set.prototype.keys === 'function' &&
-  isNative(Set.prototype.keys)
-);
-
-var setItem;
-var getItem;
-var removeItem;
-var getItemIDs;
-var addRoot;
-var removeRoot;
-var getRootIDs;
-
-if (canUseCollections) {
-  var itemMap = new Map();
-  var rootIDSet = new Set();
-
-  setItem = function(id, item) {
-    itemMap.set(id, item);
-  };
-  getItem = function(id) {
-    return itemMap.get(id);
-  };
-  removeItem = function(id) {
-    itemMap.delete(id);
-  };
-  getItemIDs = function() {
-    return Array.from(itemMap.keys());
-  };
-
-  addRoot = function(id) {
-    rootIDSet.add(id);
-  };
-  removeRoot = function(id) {
-    rootIDSet.delete(id);
-  };
-  getRootIDs = function() {
-    return Array.from(rootIDSet.keys());
-  };
-
-} else {
-  var itemByKey = {};
-  var rootByKey = {};
-
-  // Use non-numeric keys to prevent V8 performance issues:
-  // https://github.com/facebook/react/pull/7232
-  var getKeyFromID = function(id: DebugID): string {
-    return '.' + id;
-  };
-  var getIDFromKey = function(key: string): DebugID {
-    return parseInt(key.substr(1), 10);
-  };
-
-  setItem = function(id, item) {
-    var key = getKeyFromID(id);
-    itemByKey[key] = item;
-  };
-  getItem = function(id) {
-    var key = getKeyFromID(id);
-    return itemByKey[key];
-  };
-  removeItem = function(id) {
-    var key = getKeyFromID(id);
-    delete itemByKey[key];
-  };
-  getItemIDs = function() {
-    return Object.keys(itemByKey).map(getIDFromKey);
-  };
-
-  addRoot = function(id) {
-    var key = getKeyFromID(id);
-    rootByKey[key] = true;
-  };
-  removeRoot = function(id) {
-    var key = getKeyFromID(id);
-    delete rootByKey[key];
-  };
-  getRootIDs = function() {
-    return Object.keys(rootByKey).map(getIDFromKey);
-  };
-}
-
-var unmountedIDs: Array<DebugID> = [];
-
-function purgeDeep(id) {
-  var item = getItem(id);
-  if (item) {
-    var {childIDs} = item;
-    removeItem(id);
-    childIDs.forEach(purgeDeep);
-  }
-}
-
 function describeComponentFrame(name, source, ownerName) {
   return '\n    in ' + (name || 'Unknown') + (
     source ?
@@ -170,35 +36,6 @@ function describeComponentFrame(name, source, ownerName) {
   );
 }
 
-function getDisplayName(element: ?ReactElement): string {
-  if (element == null) {
-    return '#empty';
-  } else if (typeof element === 'string' || typeof element === 'number') {
-    return '#text';
-  } else if (typeof element.type === 'string') {
-    return element.type;
-  } else {
-    return element.type.displayName || element.type.name || 'Unknown';
-  }
-}
-
-function describeID(id: DebugID): string {
-  var name = ReactComponentTreeHook.getDisplayName(id);
-  var element = ReactComponentTreeHook.getElement(id);
-  var ownerID = ReactComponentTreeHook.getOwnerID(id);
-  var ownerName;
-  if (ownerID) {
-    ownerName = ReactComponentTreeHook.getDisplayName(ownerID);
-  }
-  warning(
-    element,
-    'ReactComponentTreeHook: Missing React element for debugID %s when ' +
-    'building stack',
-    id
-  );
-  return describeComponentFrame(name, element && element._source, ownerName);
-}
-
 function describeFiber(fiber : Fiber) : string {
   switch (fiber.tag) {
     case IndeterminateComponent:
@@ -219,160 +56,6 @@ function describeFiber(fiber : Fiber) : string {
 }
 
 var ReactComponentTreeHook = {
-  onSetChildren(id: DebugID, nextChildIDs: Array<DebugID>): void {
-    var item = getItem(id);
-    invariant(item, 'Item must have been set');
-    item.childIDs = nextChildIDs;
-
-    for (var i = 0; i < nextChildIDs.length; i++) {
-      var nextChildID = nextChildIDs[i];
-      var nextChild = getItem(nextChildID);
-      invariant(
-        nextChild,
-        'Expected hook events to fire for the child ' +
-        'before its parent includes it in onSetChildren().'
-      );
-      invariant(
-        nextChild.childIDs != null ||
-        typeof nextChild.element !== 'object' ||
-        nextChild.element == null,
-        'Expected onSetChildren() to fire for a container child ' +
-        'before its parent includes it in onSetChildren().'
-      );
-      invariant(
-        nextChild.isMounted,
-        'Expected onMountComponent() to fire for the child ' +
-        'before its parent includes it in onSetChildren().'
-      );
-      if (nextChild.parentID == null) {
-        nextChild.parentID = id;
-        // TODO: This shouldn't be necessary but mounting a new root during in
-        // componentWillMount currently causes not-yet-mounted components to
-        // be purged from our tree data so their parent id is missing.
-      }
-      invariant(
-        nextChild.parentID === id,
-        'Expected onBeforeMountComponent() parent and onSetChildren() to ' +
-        'be consistent (%s has parents %s and %s).',
-        nextChildID,
-        nextChild.parentID,
-        id
-      );
-    }
-  },
-
-  onBeforeMountComponent(id: DebugID, element: ReactElement, parentID: DebugID): void {
-    var item = {
-      element,
-      parentID,
-      text: null,
-      childIDs: [],
-      isMounted: false,
-      updateCount: 0,
-    };
-    setItem(id, item);
-  },
-
-  onBeforeUpdateComponent(id: DebugID, element: ReactElement): void {
-    var item = getItem(id);
-    if (!item || !item.isMounted) {
-      // We may end up here as a result of setState() in componentWillUnmount().
-      // In this case, ignore the element.
-      return;
-    }
-    item.element = element;
-  },
-
-  onMountComponent(id: DebugID): void {
-    var item = getItem(id);
-    invariant(item, 'Item must have been set');
-    item.isMounted = true;
-    var isRoot = item.parentID === 0;
-    if (isRoot) {
-      addRoot(id);
-    }
-  },
-
-  onUpdateComponent(id: DebugID): void {
-    var item = getItem(id);
-    if (!item || !item.isMounted) {
-      // We may end up here as a result of setState() in componentWillUnmount().
-      // In this case, ignore the element.
-      return;
-    }
-    item.updateCount++;
-  },
-
-  onUnmountComponent(id: DebugID): void {
-    var item = getItem(id);
-    if (item) {
-      // We need to check if it exists.
-      // `item` might not exist if it is inside an error boundary, and a sibling
-      // error boundary child threw while mounting. Then this instance never
-      // got a chance to mount, but it still gets an unmounting event during
-      // the error boundary cleanup.
-      item.isMounted = false;
-      var isRoot = item.parentID === 0;
-      if (isRoot) {
-        removeRoot(id);
-      }
-    }
-    unmountedIDs.push(id);
-  },
-
-  purgeUnmountedComponents(): void {
-    if (ReactComponentTreeHook._preventPurging) {
-      // Should only be used for testing.
-      return;
-    }
-
-    for (var i = 0; i < unmountedIDs.length; i++) {
-      var id = unmountedIDs[i];
-      purgeDeep(id);
-    }
-    unmountedIDs.length = 0;
-  },
-
-  isMounted(id: DebugID): boolean {
-    var item = getItem(id);
-    return item ? item.isMounted : false;
-  },
-
-  getCurrentStackAddendum(topElement: ?ReactElement): string {
-    var info = '';
-    if (topElement) {
-      var name = getDisplayName(topElement);
-      var owner = topElement._owner;
-      info += describeComponentFrame(
-        name,
-        topElement._source,
-        owner && getComponentName(owner)
-      );
-    }
-
-    var currentOwner = ReactCurrentOwner.current;
-    if (currentOwner) {
-      if (typeof currentOwner.tag === 'number') {
-        const workInProgress = ((currentOwner : any) : Fiber);
-        // Safe because if current owner exists, we are reconciling,
-        // and it is guaranteed to be the work-in-progress version.
-        info += ReactComponentTreeHook.getStackAddendumByWorkInProgressFiber(workInProgress);
-      } else if (typeof currentOwner._debugID === 'number') {
-        info += ReactComponentTreeHook.getStackAddendumByID(currentOwner._debugID);
-      }
-    }
-    return info;
-  },
-
-  getStackAddendumByID(id: ?DebugID): string {
-    var info = '';
-    while (id) {
-      info += describeID(id);
-      id = ReactComponentTreeHook.getParentID(id);
-    }
-    return info;
-  },
-
   // This function can only be called with a work-in-progress fiber and
   // only during begin or complete phase. Do not call it under any other
   // circumstances.
@@ -386,63 +69,392 @@ var ReactComponentTreeHook = {
     } while (node);
     return info;
   },
+};
 
-  getChildIDs(id: DebugID): Array<DebugID> {
-    var item = getItem(id);
-    return item ? item.childIDs : [];
-  },
+if (__DEV__) {
+  var ReactCurrentOwner = require('ReactCurrentOwner');
+  var invariant = require('fbjs/lib/invariant');
+  var warning = require('fbjs/lib/warning');
 
-  getDisplayName(id: DebugID): ?string {
-    var element = ReactComponentTreeHook.getElement(id);
-    if (!element) {
-      return null;
+  var isNative = function(fn) {
+    // Based on isNative() from Lodash
+    var funcToString = Function.prototype.toString;
+    var hasOwnProperty = Object.prototype.hasOwnProperty;
+    var reIsNative = RegExp('^' + funcToString
+      // Take an example native function source for comparison
+      .call(hasOwnProperty)
+      // Strip regex characters so we can use it for regex
+      .replace(/[\\^$.*+?()[\]{}|]/g, '\\$&')
+      // Remove hasOwnProperty from the template to make it generic
+      .replace(
+        /hasOwnProperty|(function).*?(?=\\\()| for .+?(?=\\\])/g,
+        '$1.*?'
+      ) + '$'
+    );
+    try {
+      var source = funcToString.call(fn);
+      return reIsNative.test(source);
+    } catch (err) {
+      return false;
     }
-    return getDisplayName(element);
-  },
+  };
 
-  getElement(id: DebugID): ?ReactElement {
+  var canUseCollections = (
+    // Array.from
+    typeof Array.from === 'function' &&
+    // Map
+    typeof Map === 'function' &&
+    isNative(Map) &&
+    // Map.prototype.keys
+    Map.prototype != null &&
+    typeof Map.prototype.keys === 'function' &&
+    isNative(Map.prototype.keys) &&
+    // Set
+    typeof Set === 'function' &&
+    isNative(Set) &&
+    // Set.prototype.keys
+    Set.prototype != null &&
+    typeof Set.prototype.keys === 'function' &&
+    isNative(Set.prototype.keys)
+  );
+
+  var setItem;
+  var getItem;
+  var removeItem;
+  var getItemIDs;
+  var addRoot;
+  var removeRoot;
+  var getRootIDs;
+
+  if (canUseCollections) {
+    var itemMap = new Map();
+    var rootIDSet = new Set();
+
+    setItem = function(id, item) {
+      itemMap.set(id, item);
+    };
+    getItem = function(id) {
+      return itemMap.get(id);
+    };
+    removeItem = function(id) {
+      itemMap.delete(id);
+    };
+    getItemIDs = function() {
+      return Array.from(itemMap.keys());
+    };
+
+    addRoot = function(id) {
+      rootIDSet.add(id);
+    };
+    removeRoot = function(id) {
+      rootIDSet.delete(id);
+    };
+    getRootIDs = function() {
+      return Array.from(rootIDSet.keys());
+    };
+
+  } else {
+    var itemByKey = {};
+    var rootByKey = {};
+
+    // Use non-numeric keys to prevent V8 performance issues:
+    // https://github.com/facebook/react/pull/7232
+    var getKeyFromID = function(id: DebugID): string {
+      return '.' + id;
+    };
+    var getIDFromKey = function(key: string): DebugID {
+      return parseInt(key.substr(1), 10);
+    };
+
+    setItem = function(id, item) {
+      var key = getKeyFromID(id);
+      itemByKey[key] = item;
+    };
+    getItem = function(id) {
+      var key = getKeyFromID(id);
+      return itemByKey[key];
+    };
+    removeItem = function(id) {
+      var key = getKeyFromID(id);
+      delete itemByKey[key];
+    };
+    getItemIDs = function() {
+      return Object.keys(itemByKey).map(getIDFromKey);
+    };
+
+    addRoot = function(id) {
+      var key = getKeyFromID(id);
+      rootByKey[key] = true;
+    };
+    removeRoot = function(id) {
+      var key = getKeyFromID(id);
+      delete rootByKey[key];
+    };
+    getRootIDs = function() {
+      return Object.keys(rootByKey).map(getIDFromKey);
+    };
+  }
+
+  var unmountedIDs: Array<DebugID> = [];
+
+  var purgeDeep = function(id) {
     var item = getItem(id);
-    return item ? item.element : null;
-  },
+    if (item) {
+      var {childIDs} = item;
+      removeItem(id);
+      childIDs.forEach(purgeDeep);
+    }
+  };
 
-  getOwnerID(id: DebugID): ?DebugID {
-    var element = ReactComponentTreeHook.getElement(id);
+  var getDisplayName = function(element: ?ReactElement): string {
+    if (element == null) {
+      return '#empty';
+    } else if (typeof element === 'string' || typeof element === 'number') {
+      return '#text';
+    } else if (typeof element.type === 'string') {
+      return element.type;
+    } else {
+      return element.type.displayName || element.type.name || 'Unknown';
+    }
+  };
+
+  var describeID = function(id: DebugID): string {
+    var name = getDisplayName((id: any));
+    var element = getElement(id);
+    var ownerID: any = getOwnerID(id);
+    var ownerName;
+    if (ownerID) {
+      ownerName = getDisplayName(ownerID);
+    }
+    warning(
+      element,
+      'ReactComponentTreeHook: Missing React element for debugID %s when ' +
+      'building stack',
+      id
+    );
+    return describeComponentFrame(name, element && element._source, ownerName);
+  };
+
+  var getOwnerID = function(id: DebugID): ?DebugID {
+    var element = getElement(id);
     if (!element || !element._owner) {
       return null;
     }
     return element._owner._debugID;
-  },
+  };
 
-  getParentID(id: DebugID): ?DebugID {
+  var getElement = function(id: DebugID): ?ReactElement {
+    var item = getItem(id);
+    return item ? item.element : null;
+  };
+
+  var getParentID = function(id: DebugID): ?DebugID {
     var item = getItem(id);
     return item ? item.parentID : null;
-  },
-
-  getSource(id: DebugID): ?Source {
-    var item = getItem(id);
-    var element = item ? item.element : null;
-    var source = element != null ? element._source : null;
-    return source;
-  },
-
-  getText(id: DebugID): ?string {
-    var element = ReactComponentTreeHook.getElement(id);
-    if (typeof element === 'string') {
-      return element;
-    } else if (typeof element === 'number') {
-      return '' + element;
-    } else {
-      return null;
+  };
+  
+  var getStackAddendumByID = function(id: ?DebugID): string {
+    var info = '';
+    while (id) {
+      info += describeID(id);
+      id = getParentID(id);
     }
-  },
+    return info;
+  };
 
-  getUpdateCount(id: DebugID): number {
-    var item = getItem(id);
-    return item ? item.updateCount : 0;
-  },
+  ReactComponentTreeHook = Object.assign({}, ReactComponentTreeHook, {
+    onSetChildren(id: DebugID, nextChildIDs: Array<DebugID>): void {
+      var item = getItem(id);
+      invariant(item, 'Item must have been set');
+      item.childIDs = nextChildIDs;
 
-  getRootIDs,
-  getRegisteredIDs: getItemIDs,
-};
+      for (var i = 0; i < nextChildIDs.length; i++) {
+        var nextChildID = nextChildIDs[i];
+        var nextChild = getItem(nextChildID);
+        invariant(
+          nextChild,
+          'Expected hook events to fire for the child ' +
+          'before its parent includes it in onSetChildren().'
+        );
+        invariant(
+          nextChild.childIDs != null ||
+          typeof nextChild.element !== 'object' ||
+          nextChild.element == null,
+          'Expected onSetChildren() to fire for a container child ' +
+          'before its parent includes it in onSetChildren().'
+        );
+        invariant(
+          nextChild.isMounted,
+          'Expected onMountComponent() to fire for the child ' +
+          'before its parent includes it in onSetChildren().'
+        );
+        if (nextChild.parentID == null) {
+          nextChild.parentID = id;
+          // TODO: This shouldn't be necessary but mounting a new root during in
+          // componentWillMount currently causes not-yet-mounted components to
+          // be purged from our tree data so their parent id is missing.
+        }
+        invariant(
+          nextChild.parentID === id,
+          'Expected onBeforeMountComponent() parent and onSetChildren() to ' +
+          'be consistent (%s has parents %s and %s).',
+          nextChildID,
+          nextChild.parentID,
+          id
+        );
+      }
+    },
+
+    onBeforeMountComponent(id: DebugID, element: ReactElement, parentID: DebugID): void {
+      var item = {
+        element,
+        parentID,
+        text: null,
+        childIDs: [],
+        isMounted: false,
+        updateCount: 0,
+      };
+      setItem(id, item);
+    },
+
+    onBeforeUpdateComponent(id: DebugID, element: ReactElement): void {
+      var item = getItem(id);
+      if (!item || !item.isMounted) {
+        // We may end up here as a result of setState() in componentWillUnmount().
+        // In this case, ignore the element.
+        return;
+      }
+      item.element = element;
+    },
+
+    onMountComponent(id: DebugID): void {
+      var item = getItem(id);
+      invariant(item, 'Item must have been set');
+      item.isMounted = true;
+      var isRoot = item.parentID === 0;
+      if (isRoot) {
+        addRoot(id);
+      }
+    },
+
+    onUpdateComponent(id: DebugID): void {
+      var item = getItem(id);
+      if (!item || !item.isMounted) {
+        // We may end up here as a result of setState() in componentWillUnmount().
+        // In this case, ignore the element.
+        return;
+      }
+      item.updateCount++;
+    },
+
+    onUnmountComponent(id: DebugID): void {
+      var item = getItem(id);
+      if (item) {
+        // We need to check if it exists.
+        // `item` might not exist if it is inside an error boundary, and a sibling
+        // error boundary child threw while mounting. Then this instance never
+        // got a chance to mount, but it still gets an unmounting event during
+        // the error boundary cleanup.
+        item.isMounted = false;
+        var isRoot = item.parentID === 0;
+        if (isRoot) {
+          removeRoot(id);
+        }
+      }
+      unmountedIDs.push(id);
+    },
+
+    purgeUnmountedComponents(): void {
+      if (ReactComponentTreeHook._preventPurging) {
+        // Should only be used for testing.
+        return;
+      }
+
+      for (var i = 0; i < unmountedIDs.length; i++) {
+        var id = unmountedIDs[i];
+        purgeDeep(id);
+      }
+      unmountedIDs.length = 0;
+    },
+
+    isMounted(id: DebugID): boolean {
+      var item = getItem(id);
+      return item ? item.isMounted : false;
+    },
+
+    getCurrentStackAddendum(topElement: ?ReactElement): string {
+      var info = '';
+      if (topElement) {
+        var name = getDisplayName(topElement);
+        var owner = topElement._owner;
+        info += describeComponentFrame(
+          name,
+          topElement._source,
+          owner && getComponentName(owner)
+        );
+      }
+
+      var currentOwner = ReactCurrentOwner.current;
+      if (currentOwner) {
+        if (typeof currentOwner.tag === 'number') {
+          const workInProgress = ((currentOwner : any) : Fiber);
+          // Safe because if current owner exists, we are reconciling,
+          // and it is guaranteed to be the work-in-progress version.
+          info += ReactComponentTreeHook.getStackAddendumByWorkInProgressFiber(workInProgress);
+        } else if (typeof currentOwner._debugID === 'number') {
+          info += getStackAddendumByID(currentOwner._debugID);
+        }
+      }
+      return info;
+    },
+
+    getStackAddendumByID,
+
+    getChildIDs(id: DebugID): Array<DebugID> {
+      var item = getItem(id);
+      return item ? item.childIDs : [];
+    },
+
+    getDisplayName(id: DebugID): ?string {
+      var element = getElement(id);
+      if (!element) {
+        return null;
+      }
+      return getDisplayName(element);
+    },
+
+    getElement,
+
+    getOwnerID,
+
+    getParentID,
+
+    getSource(id: DebugID): ?Source {
+      var item = getItem(id);
+      var element = item ? item.element : null;
+      var source = element != null ? element._source : null;
+      return source;
+    },
+
+    getText(id: DebugID): ?string {
+      var element = getElement(id);
+      if (typeof element === 'string') {
+        return element;
+      } else if (typeof element === 'number') {
+        return '' + element;
+      } else {
+        return null;
+      }
+    },
+
+    getUpdateCount(id: DebugID): number {
+      var item = getItem(id);
+      return item ? item.updateCount : 0;
+    },
+
+    getRootIDs,
+    getRegisteredIDs: getItemIDs,
+  });
+}
 
 module.exports = ReactComponentTreeHook;
diff --git a/src/renderers/shared/ReactDebugTool.js b/src/renderers/shared/ReactDebugTool.js
index 6a3781f947..bae00db165 100644
--- a/src/renderers/shared/ReactDebugTool.js
+++ b/src/renderers/shared/ReactDebugTool.js
@@ -108,22 +108,22 @@ if (__DEV__) {
   var lifeCycleTimerHasWarned = false;
 
   const clearHistory = function() {
-    ReactComponentTreeHook.purgeUnmountedComponents();
+    (ReactComponentTreeHook: any).purgeUnmountedComponents();
     ReactHostOperationHistoryHook.clearHistory();
   };
 
   const getTreeSnapshot = function(registeredIDs) {
     return registeredIDs.reduce((tree, id) => {
-      var ownerID = ReactComponentTreeHook.getOwnerID(id);
-      var parentID = ReactComponentTreeHook.getParentID(id);
+      var ownerID = (ReactComponentTreeHook: any).getOwnerID(id);
+      var parentID = (ReactComponentTreeHook: any).getParentID(id);
       tree[id] = {
-        displayName: ReactComponentTreeHook.getDisplayName(id),
-        text: ReactComponentTreeHook.getText(id),
-        updateCount: ReactComponentTreeHook.getUpdateCount(id),
-        childIDs: ReactComponentTreeHook.getChildIDs(id),
+        displayName: (ReactComponentTreeHook: any).getDisplayName(id),
+        text: (ReactComponentTreeHook: any).getText(id),
+        updateCount: (ReactComponentTreeHook: any).getUpdateCount(id),
+        childIDs: (ReactComponentTreeHook: any).getChildIDs(id),
         // Text nodes don't have owners but this is close enough.
         ownerID: ownerID ||
-          parentID && ReactComponentTreeHook.getOwnerID(parentID) ||
+          parentID && (ReactComponentTreeHook: any).getOwnerID(parentID) ||
           0,
         parentID,
       };
@@ -144,7 +144,7 @@ if (__DEV__) {
     }
 
     if (previousMeasurements.length || previousOperations.length) {
-      var registeredIDs = ReactComponentTreeHook.getRegisteredIDs();
+      var registeredIDs = (ReactComponentTreeHook: any).getRegisteredIDs();
       flushHistory.push({
         duration: performanceNow() - previousStartTime,
         measurements: previousMeasurements || [],
@@ -253,7 +253,7 @@ if (__DEV__) {
     if (!isProfiling || !canUsePerformanceMeasure) {
       return false;
     }
-    var element = ReactComponentTreeHook.getElement(debugID);
+    var element = (ReactComponentTreeHook: any).getElement(debugID);
     if (element == null || typeof element !== 'object') {
       return false;
     }
@@ -280,7 +280,7 @@ if (__DEV__) {
     }
 
     var markName = `${debugID}::${markType}`;
-    var displayName = ReactComponentTreeHook.getDisplayName(debugID) || 'Unknown';
+    var displayName = (ReactComponentTreeHook: any).getDisplayName(debugID) || 'Unknown';
 
     // Chrome has an issue of dropping markers recorded too fast:
     // https://bugs.chromium.org/p/chromium/issues/detail?id=640652
diff --git a/src/renderers/shared/stack/reconciler/ReactRef.js b/src/renderers/shared/stack/reconciler/ReactRef.js
index 120c6dddbd..1a088e32da 100644
--- a/src/renderers/shared/stack/reconciler/ReactRef.js
+++ b/src/renderers/shared/stack/reconciler/ReactRef.js
@@ -53,7 +53,7 @@ function attachRef(ref, component, owner) {
           'Stateless function components cannot be given refs. ' +
           'Attempts to access this ref will fail.%s%s',
           info,
-          ReactComponentTreeHook.getStackAddendumByID(component._debugID)
+          (ReactComponentTreeHook: any).getStackAddendumByID(component._debugID)
         );
       }
     }
diff --git a/src/shared/utils/flattenChildren.js b/src/shared/utils/flattenChildren.js
index d07630580f..7bc7d7c94a 100644
--- a/src/shared/utils/flattenChildren.js
+++ b/src/shared/utils/flattenChildren.js
@@ -58,7 +58,7 @@ function flattenSingleChildIntoContext(
           '`%s`. Child keys must be unique; when two children share a key, only ' +
           'the first child will be used.%s',
           KeyEscapeUtils.unescape(name),
-          ReactComponentTreeHook.getStackAddendumByID(selfDebugID)
+          (ReactComponentTreeHook: any).getStackAddendumByID(selfDebugID)
         );
       }
     }