diff --git a/src/renderers/dom/client/ReactDOMTreeTraversal.js b/src/renderers/dom/client/ReactDOMTreeTraversal.js
index 9cbc39f3a2..72cb838035 100644
--- a/src/renderers/dom/client/ReactDOMTreeTraversal.js
+++ b/src/renderers/dom/client/ReactDOMTreeTraversal.js
@@ -90,10 +90,10 @@ function traverseTwoPhase(inst, fn, arg) {
   }
   var i;
   for (i = path.length; i-- > 0;) {
-    fn(path[i], false, arg);
+    fn(path[i], 'captured', arg);
   }
   for (i = 0; i < path.length; i++) {
-    fn(path[i], true, arg);
+    fn(path[i], 'bubbled', arg);
   }
 }
 
@@ -118,10 +118,10 @@ function traverseEnterLeave(from, to, fn, argFrom, argTo) {
   }
   var i;
   for (i = 0; i < pathFrom.length; i++) {
-    fn(pathFrom[i], true, argFrom);
+    fn(pathFrom[i], 'bubbled', argFrom);
   }
   for (i = pathTo.length; i-- > 0;) {
-    fn(pathTo[i], false, argTo);
+    fn(pathTo[i], 'captured', argTo);
   }
 }
 
diff --git a/src/renderers/dom/client/__tests__/ReactDOMTreeTraversal-test.js b/src/renderers/dom/client/__tests__/ReactDOMTreeTraversal-test.js
index d6a5118027..d68855d30c 100644
--- a/src/renderers/dom/client/__tests__/ReactDOMTreeTraversal-test.js
+++ b/src/renderers/dom/client/__tests__/ReactDOMTreeTraversal-test.js
@@ -54,10 +54,10 @@ describe('ReactDOMTreeTraversal', () => {
   var ReactDOMTreeTraversal;
 
   var aggregatedArgs;
-  function argAggregator(inst, isUp, arg) {
+  function argAggregator(inst, phase, arg) {
     aggregatedArgs.push({
       node: ReactDOMComponentTree.getNodeFromInstance(inst),
-      isUp: isUp,
+      phase: phase,
       arg: arg,
     });
   }
@@ -82,15 +82,15 @@ describe('ReactDOMTreeTraversal', () => {
       var parent = renderParentIntoDocument();
       var target = getInst(parent.refs.P_P1_C1.refs.DIV_1);
       var expectedAggregation = [
-        {node: parent.refs.P, isUp: false, arg: ARG},
-        {node: parent.refs.P_P1, isUp: false, arg: ARG},
-        {node: parent.refs.P_P1_C1.refs.DIV, isUp: false, arg: ARG},
-        {node: parent.refs.P_P1_C1.refs.DIV_1, isUp: false, arg: ARG},
+        {node: parent.refs.P, phase: 'captured', arg: ARG},
+        {node: parent.refs.P_P1, phase: 'captured', arg: ARG},
+        {node: parent.refs.P_P1_C1.refs.DIV, phase: 'captured', arg: ARG},
+        {node: parent.refs.P_P1_C1.refs.DIV_1, phase: 'captured', arg: ARG},
 
-        {node: parent.refs.P_P1_C1.refs.DIV_1, isUp: true, arg: ARG},
-        {node: parent.refs.P_P1_C1.refs.DIV, isUp: true, arg: ARG},
-        {node: parent.refs.P_P1, isUp: true, arg: ARG},
-        {node: parent.refs.P, isUp: true, arg: ARG},
+        {node: parent.refs.P_P1_C1.refs.DIV_1, phase: 'bubbled', arg: ARG},
+        {node: parent.refs.P_P1_C1.refs.DIV, phase: 'bubbled', arg: ARG},
+        {node: parent.refs.P_P1, phase: 'bubbled', arg: ARG},
+        {node: parent.refs.P, phase: 'bubbled', arg: ARG},
       ];
       ReactDOMTreeTraversal.traverseTwoPhase(target, argAggregator, ARG);
       expect(aggregatedArgs).toEqual(expectedAggregation);
@@ -100,8 +100,8 @@ describe('ReactDOMTreeTraversal', () => {
       var parent = renderParentIntoDocument();
       var target = getInst(parent.refs.P);
       var expectedAggregation = [
-        {node: parent.refs.P, isUp: false, arg: ARG},
-        {node: parent.refs.P, isUp: true, arg: ARG},
+        {node: parent.refs.P, phase: 'captured', arg: ARG},
+        {node: parent.refs.P, phase: 'bubbled', arg: ARG},
       ];
       ReactDOMTreeTraversal.traverseTwoPhase(target, argAggregator, ARG);
       expect(aggregatedArgs).toEqual(expectedAggregation);
@@ -134,9 +134,9 @@ describe('ReactDOMTreeTraversal', () => {
       var leave = getInst(parent.refs.P_P1_C1.refs.DIV_1);
       var enter = getInst(parent.refs.P_P1_C1.refs.DIV_2);
       var expectedAggregation = [
-        {node: parent.refs.P_P1_C1.refs.DIV_1, isUp: true, arg: ARG},
+        {node: parent.refs.P_P1_C1.refs.DIV_1, phase: 'bubbled', arg: ARG},
         // enter/leave shouldn't fire anything on the parent
-        {node: parent.refs.P_P1_C1.refs.DIV_2, isUp: false, arg: ARG2},
+        {node: parent.refs.P_P1_C1.refs.DIV_2, phase: 'captured', arg: ARG2},
       ];
       ReactDOMTreeTraversal.traverseEnterLeave(
         leave, enter, argAggregator, ARG, ARG2
@@ -149,7 +149,7 @@ describe('ReactDOMTreeTraversal', () => {
       var leave = getInst(parent.refs.P_P1_C1.refs.DIV_1);
       var enter = getInst(parent.refs.P_P1_C1.refs.DIV);
       var expectedAggregation = [
-        {node: parent.refs.P_P1_C1.refs.DIV_1, isUp: true, arg: ARG},
+        {node: parent.refs.P_P1_C1.refs.DIV_1, phase: 'bubbled', arg: ARG},
       ];
       ReactDOMTreeTraversal.traverseEnterLeave(
         leave, enter, argAggregator, ARG, ARG2
@@ -162,9 +162,9 @@ describe('ReactDOMTreeTraversal', () => {
       var leave = null; // From the window or outside of the React sandbox.
       var enter = getInst(parent.refs.P_P1_C1.refs.DIV);
       var expectedAggregation = [
-        {node: parent.refs.P, isUp: false, arg: ARG2},
-        {node: parent.refs.P_P1, isUp: false, arg: ARG2},
-        {node: parent.refs.P_P1_C1.refs.DIV, isUp: false, arg: ARG2},
+        {node: parent.refs.P, phase: 'captured', arg: ARG2},
+        {node: parent.refs.P_P1, phase: 'captured', arg: ARG2},
+        {node: parent.refs.P_P1_C1.refs.DIV, phase: 'captured', arg: ARG2},
       ];
       ReactDOMTreeTraversal.traverseEnterLeave(
         leave, enter, argAggregator, ARG, ARG2
@@ -177,7 +177,7 @@ describe('ReactDOMTreeTraversal', () => {
       var leave = null; // From the window or outside of the React sandbox.
       var enter = getInst(parent.refs.P);
       var expectedAggregation = [
-        {node: parent.refs.P, isUp: false, arg: ARG2},
+        {node: parent.refs.P, phase: 'captured', arg: ARG2},
       ];
       ReactDOMTreeTraversal.traverseEnterLeave(
         leave, enter, argAggregator, ARG, ARG2
@@ -190,9 +190,9 @@ describe('ReactDOMTreeTraversal', () => {
       var enter = null; // From the window or outside of the React sandbox.
       var leave = getInst(parent.refs.P_P1_C1.refs.DIV);
       var expectedAggregation = [
-        {node: parent.refs.P_P1_C1.refs.DIV, isUp: true, arg: ARG},
-        {node: parent.refs.P_P1, isUp: true, arg: ARG},
-        {node: parent.refs.P, isUp: true, arg: ARG},
+        {node: parent.refs.P_P1_C1.refs.DIV, phase: 'bubbled', arg: ARG},
+        {node: parent.refs.P_P1, phase: 'bubbled', arg: ARG},
+        {node: parent.refs.P, phase: 'bubbled', arg: ARG},
       ];
       ReactDOMTreeTraversal.traverseEnterLeave(
         leave, enter, argAggregator, ARG, ARG2
@@ -205,9 +205,9 @@ describe('ReactDOMTreeTraversal', () => {
       var enter = null; // From the window or outside of the React sandbox.
       var leave = getInst(parent.refs.P_P1_C1.refs.DIV);
       var expectedAggregation = [
-        {node: parent.refs.P_P1_C1.refs.DIV, isUp: true, arg: ARG},
-        {node: parent.refs.P_P1, isUp: true, arg: ARG},
-        {node: parent.refs.P, isUp: true, arg: ARG},
+        {node: parent.refs.P_P1_C1.refs.DIV, phase: 'bubbled', arg: ARG},
+        {node: parent.refs.P_P1, phase: 'bubbled', arg: ARG},
+        {node: parent.refs.P, phase: 'bubbled', arg: ARG},
       ];
       ReactDOMTreeTraversal.traverseEnterLeave(
         leave, enter, argAggregator, ARG, ARG2
diff --git a/src/renderers/native/ReactNativeTreeTraversal.js b/src/renderers/native/ReactNativeTreeTraversal.js
index 52bc9f882a..988d3d7b71 100644
--- a/src/renderers/native/ReactNativeTreeTraversal.js
+++ b/src/renderers/native/ReactNativeTreeTraversal.js
@@ -110,10 +110,10 @@ function traverseEnterLeave(from, to, fn, argFrom, argTo) {
   }
   var i;
   for (i = 0; i < pathFrom.length; i++) {
-    fn(pathFrom[i], true, argFrom);
+    fn(pathFrom[i], 'bubbled', argFrom);
   }
   for (i = pathTo.length; i-- > 0;) {
-    fn(pathTo[i], false, argTo);
+    fn(pathTo[i], 'captured', argTo);
   }
 }
 
diff --git a/src/renderers/shared/stack/event/EventPropagators.js b/src/renderers/shared/stack/event/EventPropagators.js
index 3aa40994dd..da1b238416 100644
--- a/src/renderers/shared/stack/event/EventPropagators.js
+++ b/src/renderers/shared/stack/event/EventPropagators.js
@@ -38,14 +38,13 @@ function listenerAtPhase(inst, event, propagationPhase: PropagationPhases) {
  * Mutating the event's members allows us to not have to create a wrapping
  * "dispatch" object that pairs the event with the listener.
  */
-function accumulateDirectionalDispatches(inst, upwards, event) {
+function accumulateDirectionalDispatches(inst, phase, event) {
   if (__DEV__) {
     warning(
       inst,
       'Dispatching inst must not be null'
     );
   }
-  var phase = upwards ? 'bubbled' : 'captured';
   var listener = listenerAtPhase(inst, event, phase);
   if (listener) {
     event._dispatchListeners =
diff --git a/src/renderers/shared/stack/event/eventPlugins/__tests__/ResponderEventPlugin-test.js b/src/renderers/shared/stack/event/eventPlugins/__tests__/ResponderEventPlugin-test.js
index d63b741fba..584863a10f 100644
--- a/src/renderers/shared/stack/event/eventPlugins/__tests__/ResponderEventPlugin-test.js
+++ b/src/renderers/shared/stack/event/eventPlugins/__tests__/ResponderEventPlugin-test.js
@@ -389,7 +389,7 @@ describe('ResponderEventPlugin', () => {
     for (var id = start; /* until break */; id = traverse(id, stop)) {
       var ret;
       if ((!skipFirst || id !== start) && (!skipLast || id !== stop)) {
-        ret = cb(id, traverseUp, arg);
+        ret = cb(id, traverseUp ? 'bubbled': 'captured', arg);
       }
       if (ret === false || id === stop) {
         // Only break //after// visiting `stop`.
@@ -437,8 +437,8 @@ describe('ResponderEventPlugin', () => {
       traverseTwoPhase: function(target, fn, arg) {
         traverseTwoPhase(
           target._rootNodeID,
-          function(id, upwards) {
-            fn(idToInstance[id], upwards, arg);
+          function(id, phase) {
+            fn(idToInstance[id], phase, arg);
           }
         );
       },