diff --git a/src/client.js b/src/client.js
index 74b82a1256e..9ef9395d8a0 100644
--- a/src/client.js
+++ b/src/client.js
@@ -2,6 +2,7 @@
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
 Copyright 2018-2019 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -2190,7 +2191,12 @@ MatrixClient.prototype.sendReceipt = function(event, receiptType, callback) {
  * @return {module:client.Promise} Resolves: TODO
  * @return {module:http-api.MatrixError} Rejects: with an error response.
  */
-MatrixClient.prototype.sendReadReceipt = function(event, callback) {
+MatrixClient.prototype.sendReadReceipt = async function(event, callback) {
+    const eventId = event.getId();
+    const room = this.getRoom(event.getRoomId());
+    if (room && room.hasPendingEvent(eventId)) {
+        throw new Error(`Cannot set read receipt to a pending event (${eventId})`);
+    }
     return this.sendReceipt(event, "m.read", callback);
 };
 
@@ -2200,20 +2206,25 @@ MatrixClient.prototype.sendReadReceipt = function(event, callback) {
  * and displayed as a horizontal line in the timeline that is visually distinct to the
  * position of the user's own read receipt.
  * @param {string} roomId ID of the room that has been read
- * @param {string} eventId ID of the event that has been read
+ * @param {string} rmEventId ID of the event that has been read
  * @param {string} rrEvent the event tracked by the read receipt. This is here for
  * convenience because the RR and the RM are commonly updated at the same time as each
  * other. The local echo of this receipt will be done if set. Optional.
  * @return {module:client.Promise} Resolves: the empty object, {}.
  */
-MatrixClient.prototype.setRoomReadMarkers = function(roomId, eventId, rrEvent) {
-    const rmEventId = eventId;
-    let rrEventId;
+MatrixClient.prototype.setRoomReadMarkers = async function(roomId, rmEventId, rrEvent) {
+    const room = this.getRoom(roomId);
+    if (room && room.hasPendingEvent(rmEventId)) {
+        throw new Error(`Cannot set read marker to a pending event (${rmEventId})`);
+    }
 
     // Add the optional RR update, do local echo like `sendReceipt`
+    let rrEventId;
     if (rrEvent) {
         rrEventId = rrEvent.getId();
-        const room = this.getRoom(roomId);
+        if (room && room.hasPendingEvent(rrEventId)) {
+            throw new Error(`Cannot set read receipt to a pending event (${rrEventId})`);
+        }
         if (room) {
             room._addLocalEchoReceipt(this.credentials.userId, rrEvent, "m.read");
         }
diff --git a/src/models/room.js b/src/models/room.js
index 3969ede4cf3..7f5c031a33f 100644
--- a/src/models/room.js
+++ b/src/models/room.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2018, 2019 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -346,13 +347,30 @@ Room.prototype.userMayUpgradeRoom = function(userId) {
 Room.prototype.getPendingEvents = function() {
     if (this._opts.pendingEventOrdering !== "detached") {
         throw new Error(
-            "Cannot call getPendingEventList with pendingEventOrdering == " +
+            "Cannot call getPendingEvents with pendingEventOrdering == " +
                 this._opts.pendingEventOrdering);
     }
 
     return this._pendingEventList;
 };
 
+/**
+ * Check whether the pending event list contains a given event by ID.
+ *
+ * @param {string} eventId The event ID to check for.
+ * @return {boolean}
+ * @throws If <code>opts.pendingEventOrdering</code> was not 'detached'
+ */
+Room.prototype.hasPendingEvent = function(eventId) {
+    if (this._opts.pendingEventOrdering !== "detached") {
+        throw new Error(
+            "Cannot call hasPendingEvent with pendingEventOrdering == " +
+                this._opts.pendingEventOrdering);
+    }
+
+    return this._pendingEventList.some(event => event.getId() === eventId);
+};
+
 /**
  * Get the live unfiltered timeline for this room.
  *