diff --git a/spec/integ/megolm-integ.spec.ts b/spec/integ/megolm-integ.spec.ts
index a4891b702f6..d0a77a197c8 100644
--- a/spec/integ/megolm-integ.spec.ts
+++ b/spec/integ/megolm-integ.spec.ts
@@ -21,16 +21,19 @@ import * as testUtils from "../test-utils/test-utils";
 import { TestClient } from "../TestClient";
 import { logger } from "../../src/logger";
 import {
+    IClaimOTKsResult,
     IContent,
+    IDownloadKeyResult,
     IEvent,
-    IClaimOTKsResult,
     IJoinedRoom,
+    IndexedDBCryptoStore,
     ISyncResponse,
-    IDownloadKeyResult,
+    IUploadKeysRequest,
     MatrixEvent,
     MatrixEventEvent,
-    IndexedDBCryptoStore,
     Room,
+    RoomMember,
+    RoomStateEvent,
 } from "../../src/matrix";
 import { IDeviceKeys } from "../../src/crypto/dehydration";
 import { DeviceInfo } from "../../src/crypto/deviceinfo";
@@ -327,7 +330,9 @@ describe("megolm", () => {
         const room = aliceTestClient.client.getRoom(ROOM_ID)!;
         const event = room.getLiveTimeline().getEvents()[0];
         expect(event.isEncrypted()).toBe(true);
-        const decryptedEvent = await testUtils.awaitDecryption(event);
+
+        // it probably won't be decrypted yet, because it takes a while to process the olm keys
+        const decryptedEvent = await testUtils.awaitDecryption(event, { waitOnDecryptionFailure: true });
         expect(decryptedEvent.getContent().body).toEqual('42');
     });
 
@@ -873,7 +878,12 @@ describe("megolm", () => {
 
         const room = aliceTestClient.client.getRoom(ROOM_ID)!;
         await room.decryptCriticalEvents();
-        expect(room.getLiveTimeline().getEvents()[0].getContent().body).toEqual('42');
+
+        // it probably won't be decrypted yet, because it takes a while to process the olm keys
+        const decryptedEvent = await testUtils.awaitDecryption(
+            room.getLiveTimeline().getEvents()[0], { waitOnDecryptionFailure: true },
+        );
+        expect(decryptedEvent.getContent().body).toEqual('42');
 
         const exported = await aliceTestClient.client.exportRoomKeys();
 
@@ -1012,7 +1022,9 @@ describe("megolm", () => {
         const room = aliceTestClient.client.getRoom(ROOM_ID)!;
         const event = room.getLiveTimeline().getEvents()[0];
         expect(event.isEncrypted()).toBe(true);
-        const decryptedEvent = await testUtils.awaitDecryption(event);
+
+        // it probably won't be decrypted yet, because it takes a while to process the olm keys
+        const decryptedEvent = await testUtils.awaitDecryption(event, { waitOnDecryptionFailure: true });
         expect(decryptedEvent.getRoomId()).toEqual(ROOM_ID);
         expect(decryptedEvent.getContent()).toEqual({});
         expect(decryptedEvent.getClearContent()).toBeUndefined();
diff --git a/spec/test-utils/test-utils.ts b/spec/test-utils/test-utils.ts
index af87ebbe64f..21ae4d18bad 100644
--- a/spec/test-utils/test-utils.ts
+++ b/spec/test-utils/test-utils.ts
@@ -362,22 +362,28 @@ export class MockStorageApi {
  * @param {MatrixEvent} event
  * @returns {Promise} promise which resolves (to `event`) when the event has been decrypted
  */
-export async function awaitDecryption(event: MatrixEvent): Promise<MatrixEvent> {
+export async function awaitDecryption(
+    event: MatrixEvent, { waitOnDecryptionFailure = false } = {},
+): Promise<MatrixEvent> {
     // An event is not always decrypted ahead of time
     // getClearContent is a good signal to know whether an event has been decrypted
     // already
     if (event.getClearContent() !== null) {
-        return event;
+        if (waitOnDecryptionFailure && event.isDecryptionFailure()) {
+            logger.log(`${Date.now()} event ${event.getId()} got decryption error; waiting`);
+        } else {
+            return event;
+        }
     } else {
-        logger.log(`${Date.now()} event ${event.getId()} is being decrypted; waiting`);
+        logger.log(`${Date.now()} event ${event.getId()} is not yet decrypted; waiting`);
+    }
 
-        return new Promise((resolve) => {
-            event.once(MatrixEventEvent.Decrypted, (ev) => {
-                logger.log(`${Date.now()} event ${event.getId()} now decrypted`);
-                resolve(ev);
-            });
+    return new Promise((resolve) => {
+        event.once(MatrixEventEvent.Decrypted, (ev) => {
+            logger.log(`${Date.now()} event ${event.getId()} now decrypted`);
+            resolve(ev);
         });
-    }
+    });
 }
 
 export const emitPromise = (e: EventEmitter, k: string): Promise<any> => new Promise(r => e.once(k, r));
diff --git a/src/crypto/index.ts b/src/crypto/index.ts
index 7ce83a4be0b..5205fe5dfd4 100644
--- a/src/crypto/index.ts
+++ b/src/crypto/index.ts
@@ -2856,7 +2856,7 @@ export class Crypto extends TypedEventEmitter<CryptoEvent, CryptoEventHandlerMap
             // MatrixClient has already checked that this room should be encrypted,
             // so this is an unexpected situation.
             throw new Error(
-                "Room was previously configured to use encryption, but is " +
+                "Room " + roomId + " was previously configured to use encryption, but is " +
                 "no longer. Perhaps the homeserver is hiding the " +
                 "configuration event.",
             );
diff --git a/src/sync.ts b/src/sync.ts
index 15df054d603..20cab67b6eb 100644
--- a/src/sync.ts
+++ b/src/sync.ts
@@ -1362,6 +1362,18 @@ export class SyncApi {
                 }
             }
 
+            // process any crypto events *before* emitting the RoomStateEvent events. This
+            // avoids a race condition if the application tries to send a message after the
+            // state event is processed, but before crypto is enabled, which then causes the
+            // crypto layer to complain.
+            if (this.opts.crypto) {
+                for (const e of stateEvents.concat(events)) {
+                    if (e.isState() && e.getType() === EventType.RoomEncryption && e.getStateKey() === "") {
+                        await this.opts.crypto.onCryptoEvent(room, e);
+                    }
+                }
+            }
+
             try {
                 await this.injectRoomEvents(room, stateEvents, events, syncEventData.fromCache);
             } catch (e) {
@@ -1389,21 +1401,11 @@ export class SyncApi {
 
             this.processEventsForNotifs(room, events);
 
-            const processRoomEvent = async (e): Promise<void> => {
-                client.emit(ClientEvent.Event, e);
-                if (e.isState() && e.getType() == "m.room.encryption" && this.opts.crypto) {
-                    await this.opts.crypto.onCryptoEvent(room, e);
-                }
-            };
-
-            await utils.promiseMapSeries(stateEvents, processRoomEvent);
-            await utils.promiseMapSeries(events, processRoomEvent);
-            ephemeralEvents.forEach(function(e) {
-                client.emit(ClientEvent.Event, e);
-            });
-            accountDataEvents.forEach(function(e) {
-                client.emit(ClientEvent.Event, e);
-            });
+            const emitEvent = (e: MatrixEvent): boolean => client.emit(ClientEvent.Event, e);
+            stateEvents.forEach(emitEvent);
+            events.forEach(emitEvent);
+            ephemeralEvents.forEach(emitEvent);
+            accountDataEvents.forEach(emitEvent);
 
             // Decrypt only the last message in all rooms to make sure we can generate a preview
             // And decrypt all events after the recorded read receipt to ensure an accurate