diff --git a/examples/node/app.js b/examples/node/app.js
index 46220a065..90396b56b 100644
--- a/examples/node/app.js
+++ b/examples/node/app.js
@@ -288,7 +288,7 @@ function printMemberList(room) {
 }
 
 function printRoomInfo(room) {
-    var eventDict = room.currentState.events;
+    var eventMap = room.currentState.events;
     var eTypeHeader = "    Event Type(state_key)    ";
     var sendHeader = "        Sender        ";
     // pad content to 100
@@ -300,14 +300,15 @@ function printRoomInfo(room) {
     var contentHeader = padSide + "Content" + padSide;
     print(eTypeHeader+sendHeader+contentHeader);
     print(new Array(100).join("-"));
-    Object.keys(eventDict).forEach(function(eventType) {
+    eventMap.keys().forEach(function(eventType) {
         if (eventType === "m.room.member") { return; } // use /members instead.
-        Object.keys(eventDict[eventType]).forEach(function(stateKey) {
+        var eventEventMap = eventMap.get(eventType);
+        eventEventMap.keys().forEach(function(stateKey) {
             var typeAndKey = eventType + (
                 stateKey.length > 0 ? "("+stateKey+")" : ""
             );
             var typeStr = fixWidth(typeAndKey, eTypeHeader.length);
-            var event = eventDict[eventType][stateKey];
+            var event = eventEventMap.get(stateKey);
             var sendStr = fixWidth(event.getSender(), sendHeader.length);
             var contentStr = fixWidth(
                 JSON.stringify(event.getContent()), contentHeader.length
diff --git a/src/models/room-state.js b/src/models/room-state.js
index a7d1072ef..cbcf0b29d 100644
--- a/src/models/room-state.js
+++ b/src/models/room-state.js
@@ -68,9 +68,7 @@ export function RoomState(roomId, oobMemberFlags = undefined) {
     this.members = {
         // userId: RoomMember
     };
-    this.events = {
-        // eventType: { stateKey: MatrixEvent }
-    };
+    this.events = new Map(); // { eventType: { stateKey: MatrixEvent } }
     this.paginationToken = null;
 
     this._sentinels = {
@@ -211,14 +209,14 @@ RoomState.prototype.getSentinelMember = function(userId) {
  * <code>undefined</code>, else a single event (or null if no match found).
  */
 RoomState.prototype.getStateEvents = function(eventType, stateKey) {
-    if (!this.events[eventType]) {
+    if (!this.events.has(eventType)) {
         // no match
         return stateKey === undefined ? [] : null;
     }
     if (stateKey === undefined) { // return all values
-        return utils.values(this.events[eventType]);
+        return Array.from(this.events.get(eventType).values());
     }
-    const event = this.events[eventType][stateKey];
+    const event = this.events.get(eventType).get(stateKey);
     return event ? event : null;
 };
 
@@ -238,9 +236,8 @@ RoomState.prototype.clone = function() {
     const status = this._oobMemberFlags.status;
     this._oobMemberFlags.status = OOB_STATUS_NOTSTARTED;
 
-    Object.values(this.events).forEach((eventsByStateKey) => {
-        const eventsForType = Object.values(eventsByStateKey);
-        copy.setStateEvents(eventsForType);
+    Array.from(this.events.values()).forEach((eventsByStateKey) => {
+        copy.setStateEvents(Array.from(eventsByStateKey.values()));
     });
 
     // Ugly hack: see above
@@ -276,8 +273,8 @@ RoomState.prototype.clone = function() {
  */
 RoomState.prototype.setUnknownStateEvents = function(events) {
     const unknownStateEvents = events.filter((event) => {
-        return this.events[event.getType()] === undefined ||
-            this.events[event.getType()][event.getStateKey()] === undefined;
+        return !this.events.has(event.getType()) ||
+            !this.events.get(event.getType()).has(event.getStateKey());
     });
 
     this.setStateEvents(unknownStateEvents);
@@ -386,15 +383,15 @@ RoomState.prototype._getOrCreateMember = function(userId, event) {
 };
 
 RoomState.prototype._setStateEvent = function(event) {
-    if (this.events[event.getType()] === undefined) {
-        this.events[event.getType()] = {};
+    if (!this.events.has(event.getType())) {
+        this.events.set(event.getType(), new Map());
     }
-    this.events[event.getType()][event.getStateKey()] = event;
+    this.events.get(event.getType()).set(event.getStateKey(), event);
 };
 
 RoomState.prototype._getStateEventMatching = function(event) {
-    if (!this.events[event.getType()]) return null;
-    return this.events[event.getType()][event.getStateKey()];
+    if (!this.events.has(event.getType())) return null;
+    return this.events.get(event.getType()).get(event.getStateKey());
 };
 
 RoomState.prototype._updateMember = function(member) {