diff --git a/src/isomorphic/classic/element/ReactDebugCurrentFrame.js b/src/isomorphic/classic/element/ReactDebugCurrentFrame.js
index eb1d1ecaa4..e5e966b706 100644
--- a/src/isomorphic/classic/element/ReactDebugCurrentFrame.js
+++ b/src/isomorphic/classic/element/ReactDebugCurrentFrame.js
@@ -14,13 +14,13 @@
 
 import type { Fiber } from 'ReactFiber';
 import type { DebugID } from 'ReactInstanceType';
-import type { ComponentTreeHookDevType } from '../../hooks/ReactComponentTreeHook';
+import type { ComponentTreeHookDevType } from 'ReactComponentTreeHook';
 
 const ReactDebugCurrentFrame = {};
 
 if (__DEV__) {
   // how do a state that ReactComponentTreeHook is using the ComponentTreeHookDevType type?
-  const ReactComponentTreeHook: ComponentTreeHookDevType = require('ReactComponentTreeHook');
+  const ReactComponentTreeHook: ComponentTreeHookDevType = (require('ReactComponentTreeHook'): any);
   const {
     getStackAddendumByID,
     getStackAddendumByWorkInProgressFiber,
diff --git a/src/isomorphic/hooks/ReactComponentTreeHook.js b/src/isomorphic/hooks/ReactComponentTreeHook.js
index c7e2141b34..5d8cdf616d 100644
--- a/src/isomorphic/hooks/ReactComponentTreeHook.js
+++ b/src/isomorphic/hooks/ReactComponentTreeHook.js
@@ -71,6 +71,7 @@ export type ComponentTreeHookDevType = {
   getUpdateCount: (DebugID) => any,
   getChildIDs: (DebugID) => any,
   getRegisteredIDs: () => any,
+  getElement: () => any,
 };
 
 var ReactComponentTreeHook: ComponentTreeHookType = {
diff --git a/src/renderers/shared/ReactDebugTool.js b/src/renderers/shared/ReactDebugTool.js
index 1d07610ade..b0e91811e0 100644
--- a/src/renderers/shared/ReactDebugTool.js
+++ b/src/renderers/shared/ReactDebugTool.js
@@ -22,6 +22,7 @@ var warning = require('fbjs/lib/warning');
 import type { ReactElement } from 'ReactElementType';
 import type { DebugID } from 'ReactInstanceType';
 import type { Operation } from 'ReactHostOperationHistoryHook';
+import type { ComponentTreeHookDevType } from 'ReactComponentTreeHook';
 
 type Hook = any;
 
@@ -68,7 +69,7 @@ var ReactDebugTool = ((null: any): typeof ReactDebugTool);
 if (__DEV__) {
   const hooks = [];
   const didHookThrowForEvent = {};
-  const ReactComponentTreeHook = require('react/lib/ReactComponentTreeHook');
+  const ReactComponentTreeHook: ComponentTreeHookDevType = (require('react/lib/ReactComponentTreeHook'): any);
   const {
     purgeUnmountedComponents,
     getOwnerID,
@@ -78,6 +79,7 @@ if (__DEV__) {
     getUpdateCount,
     getChildIDs,
     getRegisteredIDs,
+    getElement,
   } = ReactComponentTreeHook;
 
   const callHook = function(event, fn, context, arg1, arg2, arg3, arg4, arg5) {
@@ -118,24 +120,22 @@ if (__DEV__) {
   var lifeCycleTimerHasWarned = false;
 
   const clearHistory = function() {
-    if (purgeUnmountedComponents) {
-      purgeUnmountedComponents();
-    }
+    purgeUnmountedComponents();
     ReactHostOperationHistoryHook.clearHistory();
   };
 
   const getTreeSnapshot = function(registeredIDs) {
-    return registeredIDs && registeredIDs.reduce((tree, id) => {
-      var ownerID = getOwnerID && getOwnerID(id);
-      var parentID = getParentID && getParentID(id);
+    return registeredIDs.reduce((tree, id) => {
+      var ownerID = getOwnerID(id);
+      var parentID = getParentID(id);
       tree[id] = {
-        displayName: getDisplayName && getDisplayName(id),
-        text: getText && getText(id),
-        updateCount: getUpdateCount && getUpdateCount(id),
-        childIDs: getChildIDs && getChildIDs(id),
+        displayName: getDisplayName(id),
+        text: getText(id),
+        updateCount: getUpdateCount(id),
+        childIDs: getChildIDs(id),
         // Text nodes don't have owners but this is close enough.
         ownerID: ownerID ||
-          parentID && getOwnerID && getOwnerID(parentID) ||
+          parentID && getOwnerID(parentID) ||
           0,
         parentID,
       };
@@ -156,16 +156,14 @@ if (__DEV__) {
     }
 
     if (previousMeasurements.length || previousOperations.length) {
-      var registeredIDs = getRegisteredIDs && getRegisteredIDs();
+      var registeredIDs = getRegisteredIDs();
 
-      if (registeredIDs) {
-        flushHistory.push({
-          duration: performanceNow() - previousStartTime,
-          measurements: previousMeasurements || [],
-          operations: previousOperations || [],
-          treeSnapshot: getTreeSnapshot(registeredIDs),
-        });
-      }
+      flushHistory.push({
+        duration: performanceNow() - previousStartTime,
+        measurements: previousMeasurements || [],
+        operations: previousOperations || [],
+        treeSnapshot: getTreeSnapshot(registeredIDs),
+      });
     }
 
     clearHistory();
@@ -268,7 +266,7 @@ if (__DEV__) {
     if (!isProfiling || !canUsePerformanceMeasure) {
       return false;
     }
-    var element = (ReactComponentTreeHook: any).getElement(debugID);
+    var element = getElement(debugID);
     if (element == null || typeof element !== 'object') {
       return false;
     }
@@ -295,7 +293,7 @@ if (__DEV__) {
     }
 
     var markName = `${debugID}::${markType}`;
-    var displayName = getDisplayName && getDisplayName(debugID) || 'Unknown';
+    var displayName = 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 155dab6c80..7f2e5c4567 100644
--- a/src/renderers/shared/stack/reconciler/ReactRef.js
+++ b/src/renderers/shared/stack/reconciler/ReactRef.js
@@ -16,6 +16,7 @@ var ReactOwner = require('ReactOwner');
 
 import type { ReactInstance } from 'ReactInstanceType';
 import type { ReactElement } from 'ReactElementType';
+import type { ComponentTreeHookDevType } from 'ReactComponentTreeHook';
 
 var ReactRef = {};
 
@@ -23,7 +24,7 @@ if (__DEV__) {
   var ReactCompositeComponentTypes = require('ReactCompositeComponentTypes');
   var {
     getStackAddendumByID,
-  } = require('react/lib/ReactComponentTreeHook');
+  }: ComponentTreeHookDevType = (require('react/lib/ReactComponentTreeHook'): any);
   var warning = require('fbjs/lib/warning');
 
   var warnedAboutStatelessRefs = {};
@@ -55,7 +56,7 @@ function attachRef(ref, component, owner) {
           'Stateless function components cannot be given refs. ' +
           'Attempts to access this ref will fail.%s%s',
           info,
-          getStackAddendumByID && getStackAddendumByID(component._debugID)
+          getStackAddendumByID(component._debugID)
         );
       }
     }
diff --git a/src/shared/utils/flattenChildren.js b/src/shared/utils/flattenChildren.js
index f2992becdf..2a8165c829 100644
--- a/src/shared/utils/flattenChildren.js
+++ b/src/shared/utils/flattenChildren.js
@@ -12,6 +12,8 @@
 
 'use strict';
 
+import type { ComponentTreeHookDevType } from 'ReactComponentTreeHook';
+
 var KeyEscapeUtils = require('KeyEscapeUtils');
 var traverseAllChildren = require('traverseAllChildren');
 var warning = require('fbjs/lib/warning');
@@ -51,7 +53,7 @@ function flattenSingleChildIntoContext(
       if (!ReactComponentTreeHook) {
         ReactComponentTreeHook = require('react/lib/ReactComponentTreeHook');
       }
-      const { getStackAddendumByID } = ReactComponentTreeHook;
+      const { getStackAddendumByID }: ComponentTreeHookDevType = (ReactComponentTreeHook: any);
 
       if (!keyUnique) {
         warning(
@@ -60,7 +62,7 @@ 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),
-          getStackAddendumByID && getStackAddendumByID(selfDebugID)
+          getStackAddendumByID(selfDebugID)
         );
       }
     }