diff --git a/src/renderers/__tests__/ReactStatelessComponent-test.js b/src/renderers/__tests__/ReactStatelessComponent-test.js
index c8d67c7bbfc2c..577a6c1ee13d6 100644
--- a/src/renderers/__tests__/ReactStatelessComponent-test.js
+++ b/src/renderers/__tests__/ReactStatelessComponent-test.js
@@ -295,6 +295,43 @@ describe('ReactStatelessComponent', () => {
     console.error.calls.reset();
   });
 
+  // This guards against a regression caused by clearing the current debug fiber.
+  // https://github.com/facebook/react/issues/10831
+  it('should warn when giving a function ref with context', () => {
+    spyOn(console, 'error');
+
+    function Child() {
+      return null;
+    }
+    Child.contextTypes = {
+      foo: PropTypes.string,
+    };
+
+    class Parent extends React.Component {
+      static childContextTypes = {
+        foo: PropTypes.string,
+      };
+      getChildContext() {
+        return {
+          foo: 'bar',
+        };
+      }
+      render() {
+        return <Child ref={function() {}} />;
+      }
+    }
+
+    ReactTestUtils.renderIntoDocument(<Parent />);
+    expectDev(console.error.calls.count()).toBe(1);
+    expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
+      'Warning: Stateless function components cannot be given refs. ' +
+        'Attempts to access this ref will fail.\n\nCheck the render method ' +
+        'of `Parent`.\n' +
+        '    in Child (at **)\n' +
+        '    in Parent (at **)',
+    );
+  });
+
   it('should provide a null ref', () => {
     function Child() {
       return <div />;
diff --git a/src/renderers/shared/fiber/ReactDebugCurrentFiber.js b/src/renderers/shared/fiber/ReactDebugCurrentFiber.js
index a34e1d14e5e2b..16a4096bd7282 100644
--- a/src/renderers/shared/fiber/ReactDebugCurrentFiber.js
+++ b/src/renderers/shared/fiber/ReactDebugCurrentFiber.js
@@ -55,9 +55,13 @@ function resetCurrentFiber() {
   ReactDebugCurrentFiber.phase = null;
 }
 
-function setCurrentFiber(fiber: Fiber | null, phase: LifeCyclePhase | null) {
+function setCurrentFiber(fiber: Fiber) {
   ReactDebugCurrentFrame.getCurrentStack = getCurrentFiberStackAddendum;
   ReactDebugCurrentFiber.current = fiber;
+  ReactDebugCurrentFiber.phase = null;
+}
+
+function setCurrentPhase(phase: LifeCyclePhase | null) {
   ReactDebugCurrentFiber.phase = phase;
 }
 
@@ -66,6 +70,7 @@ var ReactDebugCurrentFiber = {
   phase: (null: LifeCyclePhase | null),
   resetCurrentFiber,
   setCurrentFiber,
+  setCurrentPhase,
   getCurrentFiberOwnerName,
   getCurrentFiberStackAddendum,
 };
diff --git a/src/renderers/shared/fiber/ReactFiberBeginWork.js b/src/renderers/shared/fiber/ReactFiberBeginWork.js
index 9b945305d4b05..ed81a1d778944 100644
--- a/src/renderers/shared/fiber/ReactFiberBeginWork.js
+++ b/src/renderers/shared/fiber/ReactFiberBeginWork.js
@@ -207,9 +207,9 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
 
     if (__DEV__) {
       ReactCurrentOwner.current = workInProgress;
-      ReactDebugCurrentFiber.setCurrentFiber(workInProgress, 'render');
+      ReactDebugCurrentFiber.setCurrentPhase('render');
       nextChildren = fn(nextProps, context);
-      ReactDebugCurrentFiber.setCurrentFiber(workInProgress, null);
+      ReactDebugCurrentFiber.setCurrentPhase(null);
     } else {
       nextChildren = fn(nextProps, context);
     }
@@ -281,9 +281,9 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     ReactCurrentOwner.current = workInProgress;
     let nextChildren;
     if (__DEV__) {
-      ReactDebugCurrentFiber.setCurrentFiber(workInProgress, 'render');
+      ReactDebugCurrentFiber.setCurrentPhase('render');
       nextChildren = instance.render();
-      ReactDebugCurrentFiber.setCurrentFiber(workInProgress, null);
+      ReactDebugCurrentFiber.setCurrentPhase(null);
     } else {
       nextChildren = instance.render();
     }
@@ -725,10 +725,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
       return bailoutOnLowPriority(current, workInProgress);
     }
 
-    if (__DEV__) {
-      ReactDebugCurrentFiber.setCurrentFiber(workInProgress, null);
-    }
-
     switch (workInProgress.tag) {
       case IndeterminateComponent:
         return mountIndeterminateComponent(
diff --git a/src/renderers/shared/fiber/ReactFiberCompleteWork.js b/src/renderers/shared/fiber/ReactFiberCompleteWork.js
index 41393a19e22ef..451e379965da1 100644
--- a/src/renderers/shared/fiber/ReactFiberCompleteWork.js
+++ b/src/renderers/shared/fiber/ReactFiberCompleteWork.js
@@ -42,10 +42,6 @@ var {
 var {Placement, Ref, Update} = ReactTypeOfSideEffect;
 var {OffscreenPriority} = ReactPriorityLevel;
 
-if (__DEV__) {
-  var ReactDebugCurrentFiber = require('ReactDebugCurrentFiber');
-}
-
 var invariant = require('fbjs/lib/invariant');
 
 module.exports = function<T, P, I, TI, PI, C, CX, PL>(
@@ -187,10 +183,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     workInProgress: Fiber,
     renderPriority: PriorityLevel,
   ): Fiber | null {
-    if (__DEV__) {
-      ReactDebugCurrentFiber.setCurrentFiber(workInProgress, null);
-    }
-
     // Get the latest props.
     let newProps = workInProgress.pendingProps;
     if (newProps === null) {
diff --git a/src/renderers/shared/fiber/ReactFiberContext.js b/src/renderers/shared/fiber/ReactFiberContext.js
index fb0d4dda3ade9..8c5bb96526177 100644
--- a/src/renderers/shared/fiber/ReactFiberContext.js
+++ b/src/renderers/shared/fiber/ReactFiberContext.js
@@ -89,7 +89,6 @@ exports.getMaskedContext = function(
 
   if (__DEV__) {
     const name = getComponentName(workInProgress) || 'Unknown';
-    ReactDebugCurrentFiber.setCurrentFiber(workInProgress, null);
     checkPropTypes(
       contextTypes,
       context,
@@ -97,7 +96,6 @@ exports.getMaskedContext = function(
       name,
       ReactDebugCurrentFiber.getCurrentFiberStackAddendum,
     );
-    ReactDebugCurrentFiber.resetCurrentFiber();
   }
 
   // Cache unmasked context so we can avoid recreating masked context unless necessary.
@@ -153,11 +151,7 @@ exports.pushTopLevelContextObject = function(
   push(didPerformWorkStackCursor, didChange, fiber);
 };
 
-function processChildContext(
-  fiber: Fiber,
-  parentContext: Object,
-  isReconciling: boolean,
-): Object {
+function processChildContext(fiber: Fiber, parentContext: Object): Object {
   const instance = fiber.stateNode;
   const childContextTypes = fiber.type.childContextTypes;
 
@@ -184,11 +178,11 @@ function processChildContext(
 
   let childContext;
   if (__DEV__) {
-    ReactDebugCurrentFiber.setCurrentFiber(fiber, 'getChildContext');
+    ReactDebugCurrentFiber.setCurrentPhase('getChildContext');
     startPhaseTimer(fiber, 'getChildContext');
     childContext = instance.getChildContext();
     stopPhaseTimer();
-    ReactDebugCurrentFiber.resetCurrentFiber();
+    ReactDebugCurrentFiber.setCurrentPhase(null);
   } else {
     childContext = instance.getChildContext();
   }
@@ -202,21 +196,18 @@ function processChildContext(
   }
   if (__DEV__) {
     const name = getComponentName(fiber) || 'Unknown';
-    // We can only provide accurate element stacks if we pass work-in-progress tree
-    // during the begin or complete phase. However currently this function is also
-    // called from unstable_renderSubtree legacy implementation. In this case it unsafe to
-    // assume anything about the given fiber. We won't pass it down if we aren't sure.
-    // TODO: remove this hack when we delete unstable_renderSubtree in Fiber.
-    const workInProgress = isReconciling ? fiber : null;
-    ReactDebugCurrentFiber.setCurrentFiber(workInProgress, null);
     checkPropTypes(
       childContextTypes,
       childContext,
       'child context',
       name,
+      // In practice, there is one case in which we won't get a stack. It's when
+      // somebody calls unstable_renderSubtreeIntoContainer() and we process
+      // context from the parent component instance. The stack will be missing
+      // because it's outside of the reconciliation, and so the pointer has not
+      // been set. This is rare and doesn't matter. We'll also remove that API.
       ReactDebugCurrentFiber.getCurrentFiberStackAddendum,
     );
-    ReactDebugCurrentFiber.resetCurrentFiber();
   }
 
   return {...parentContext, ...childContext};
@@ -264,11 +255,7 @@ exports.invalidateContextProvider = function(
     // Merge parent and own context.
     // Skip this if we're not updating due to sCU.
     // This avoids unnecessarily recomputing memoized values.
-    const mergedContext = processChildContext(
-      workInProgress,
-      previousContext,
-      true,
-    );
+    const mergedContext = processChildContext(workInProgress, previousContext);
     instance.__reactInternalMemoizedMergedChildContext = mergedContext;
 
     // Replace the old (or empty) context with the new one.
diff --git a/src/renderers/shared/fiber/ReactFiberReconciler.js b/src/renderers/shared/fiber/ReactFiberReconciler.js
index 8b9fa1d3df7e0..23738f3c40143 100644
--- a/src/renderers/shared/fiber/ReactFiberReconciler.js
+++ b/src/renderers/shared/fiber/ReactFiberReconciler.js
@@ -181,7 +181,7 @@ export type Reconciler<C, I, TI> = {
 getContextForSubtree._injectFiber(function(fiber: Fiber) {
   const parentContext = findCurrentUnmaskedContext(fiber);
   return isContextProvider(fiber)
-    ? processChildContext(fiber, parentContext, false)
+    ? processChildContext(fiber, parentContext)
     : parentContext;
 });
 
diff --git a/src/renderers/shared/fiber/ReactFiberScheduler.js b/src/renderers/shared/fiber/ReactFiberScheduler.js
index dcaea4aa86092..495bb550de265 100644
--- a/src/renderers/shared/fiber/ReactFiberScheduler.js
+++ b/src/renderers/shared/fiber/ReactFiberScheduler.js
@@ -317,7 +317,7 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
   function commitAllHostEffects() {
     while (nextEffect !== null) {
       if (__DEV__) {
-        ReactDebugCurrentFiber.setCurrentFiber(nextEffect, null);
+        ReactDebugCurrentFiber.setCurrentFiber(nextEffect);
         recordEffect();
       }
 
@@ -615,7 +615,13 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
       // means that we don't need an additional field on the work in
       // progress.
       const current = workInProgress.alternate;
+      if (__DEV__) {
+        ReactDebugCurrentFiber.setCurrentFiber(workInProgress);
+      }
       const next = completeWork(current, workInProgress, nextPriorityLevel);
+      if (__DEV__) {
+        ReactDebugCurrentFiber.resetCurrentFiber();
+      }
 
       const returnFiber = workInProgress.return;
       const siblingFiber = workInProgress.sibling;
@@ -706,8 +712,12 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     // See if beginning this work spawns more work.
     if (__DEV__) {
       startWorkTimer(workInProgress);
+      ReactDebugCurrentFiber.setCurrentFiber(workInProgress);
     }
     let next = beginWork(current, workInProgress, nextPriorityLevel);
+    if (__DEV__) {
+      ReactDebugCurrentFiber.resetCurrentFiber();
+    }
     if (__DEV__ && ReactFiberInstrumentation.debugTool) {
       ReactFiberInstrumentation.debugTool.onBeginWork(workInProgress);
     }
@@ -718,9 +728,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     }
 
     ReactCurrentOwner.current = null;
-    if (__DEV__) {
-      ReactDebugCurrentFiber.resetCurrentFiber();
-    }
 
     return next;
   }
@@ -735,8 +742,12 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     // See if beginning this work spawns more work.
     if (__DEV__) {
       startWorkTimer(workInProgress);
+      ReactDebugCurrentFiber.setCurrentFiber(workInProgress);
     }
     let next = beginFailedWork(current, workInProgress, nextPriorityLevel);
+    if (__DEV__) {
+      ReactDebugCurrentFiber.resetCurrentFiber();
+    }
     if (__DEV__ && ReactFiberInstrumentation.debugTool) {
       ReactFiberInstrumentation.debugTool.onBeginWork(workInProgress);
     }
@@ -747,9 +758,6 @@ module.exports = function<T, P, I, TI, PI, C, CX, PL>(
     }
 
     ReactCurrentOwner.current = null;
-    if (__DEV__) {
-      ReactDebugCurrentFiber.resetCurrentFiber();
-    }
 
     return next;
   }