diff --git a/spec/integ/megolm-integ.spec.js b/spec/integ/megolm-integ.spec.js
index 73fcfa81d8e..4c60f26fcc5 100644
--- a/spec/integ/megolm-integ.spec.js
+++ b/spec/integ/megolm-integ.spec.js
@@ -618,6 +618,9 @@ describe("megolm", function() {
             aliceTestClient.httpBackend.when(
                 'PUT', '/sendToDevice/org.matrix.room_key.withheld/',
             ).respond(200, {});
+            aliceTestClient.httpBackend.when(
+                'PUT', '/sendToDevice/m.room_key.withheld/',
+            ).respond(200, {});
 
             return Promise.all([
                 aliceTestClient.client.sendTextMessage(ROOM_ID, 'test'),
@@ -718,6 +721,9 @@ describe("megolm", function() {
             aliceTestClient.httpBackend.when(
                 'PUT', '/sendToDevice/org.matrix.room_key.withheld/',
             ).respond(200, {});
+            aliceTestClient.httpBackend.when(
+                'PUT', '/sendToDevice/m.room_key.withheld/',
+            ).respond(200, {});
 
             return Promise.all([
                 aliceTestClient.client.sendTextMessage(ROOM_ID, 'test2'),
diff --git a/spec/unit/crypto/algorithms/megolm.spec.js b/spec/unit/crypto/algorithms/megolm.spec.js
index d949b1bed58..c63031f65a4 100644
--- a/spec/unit/crypto/algorithms/megolm.spec.js
+++ b/spec/unit/crypto/algorithms/megolm.spec.js
@@ -462,7 +462,7 @@ describe("MegolmDecryption", function() {
         let run = false;
         aliceClient.sendToDevice = async (msgtype, contentMap) => {
             run = true;
-            expect(msgtype).toBe("org.matrix.room_key.withheld");
+            expect(msgtype).toMatch(/^(org.matrix|m).room_key.withheld$/);
             delete contentMap["@bob:example.com"].bobdevice1.session_id;
             delete contentMap["@bob:example.com"].bobdevice2.session_id;
             expect(contentMap).toStrictEqual({
@@ -572,7 +572,7 @@ describe("MegolmDecryption", function() {
 
         const sendPromise = new Promise((resolve, reject) => {
             aliceClient.sendToDevice = async (msgtype, contentMap) => {
-                expect(msgtype).toBe("org.matrix.room_key.withheld");
+                expect(msgtype).toMatch(/^(org.matrix|m).room_key.withheld$/);
                 expect(contentMap).toStrictEqual({
                     '@bob:example.com': {
                         bobdevice: {
@@ -619,7 +619,7 @@ describe("MegolmDecryption", function() {
             content: {
                 algorithm: "m.megolm.v1.aes-sha2",
                 room_id: roomId,
-                session_id: "session_id",
+                session_id: "session_id1",
                 sender_key: bobDevice.deviceCurve25519Key,
                 code: "m.blacklisted",
                 reason: "You have been blocked",
@@ -636,7 +636,34 @@ describe("MegolmDecryption", function() {
                 ciphertext: "blablabla",
                 device_id: "bobdevice",
                 sender_key: bobDevice.deviceCurve25519Key,
-                session_id: "session_id",
+                session_id: "session_id1",
+            },
+        }))).rejects.toThrow("The sender has blocked you.");
+
+        aliceClient.crypto.onToDeviceEvent(new MatrixEvent({
+            type: "m.room_key.withheld",
+            sender: "@bob:example.com",
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                room_id: roomId,
+                session_id: "session_id2",
+                sender_key: bobDevice.deviceCurve25519Key,
+                code: "m.blacklisted",
+                reason: "You have been blocked",
+            },
+        }));
+
+        await expect(aliceClient.crypto.decryptEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            event_id: "$event",
+            room_id: roomId,
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                ciphertext: "blablabla",
+                device_id: "bobdevice",
+                sender_key: bobDevice.deviceCurve25519Key,
+                session_id: "session_id2",
             },
         }))).rejects.toThrow("The sender has blocked you.");
     });
@@ -665,7 +692,7 @@ describe("MegolmDecryption", function() {
             content: {
                 algorithm: "m.megolm.v1.aes-sha2",
                 room_id: roomId,
-                session_id: "session_id",
+                session_id: "session_id1",
                 sender_key: bobDevice.deviceCurve25519Key,
                 code: "m.no_olm",
                 reason: "Unable to establish a secure channel.",
@@ -686,7 +713,39 @@ describe("MegolmDecryption", function() {
                 ciphertext: "blablabla",
                 device_id: "bobdevice",
                 sender_key: bobDevice.deviceCurve25519Key,
-                session_id: "session_id",
+                session_id: "session_id1",
+            },
+            origin_server_ts: now,
+        }))).rejects.toThrow("The sender was unable to establish a secure channel.");
+
+        aliceClient.crypto.onToDeviceEvent(new MatrixEvent({
+            type: "m.room_key.withheld",
+            sender: "@bob:example.com",
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                room_id: roomId,
+                session_id: "session_id2",
+                sender_key: bobDevice.deviceCurve25519Key,
+                code: "m.no_olm",
+                reason: "Unable to establish a secure channel.",
+            },
+        }));
+
+        await new Promise((resolve) => {
+            setTimeout(resolve, 100);
+        });
+
+        await expect(aliceClient.crypto.decryptEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            event_id: "$event",
+            room_id: roomId,
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                ciphertext: "blablabla",
+                device_id: "bobdevice",
+                sender_key: bobDevice.deviceCurve25519Key,
+                session_id: "session_id2",
             },
             origin_server_ts: now,
         }))).rejects.toThrow("The sender was unable to establish a secure channel.");
diff --git a/src/crypto/algorithms/megolm.ts b/src/crypto/algorithms/megolm.ts
index 31beb64ef2c..f960dd4f15e 100644
--- a/src/crypto/algorithms/megolm.ts
+++ b/src/crypto/algorithms/megolm.ts
@@ -709,6 +709,7 @@ class MegolmEncryption extends EncryptionAlgorithm {
         }
 
         await this.baseApis.sendToDevice("org.matrix.room_key.withheld", contentMap);
+        await this.baseApis.sendToDevice("m.room_key.withheld", contentMap);
 
         // record the fact that we notified these blocked devices
         for (const userId of Object.keys(contentMap)) {
diff --git a/src/crypto/index.ts b/src/crypto/index.ts
index 14771da4312..f5676f37e65 100644
--- a/src/crypto/index.ts
+++ b/src/crypto/index.ts
@@ -3115,7 +3115,8 @@ export class Crypto extends TypedEventEmitter<CryptoEvent, CryptoEventHandlerMap
                 this.secretStorage.onRequestReceived(event);
             } else if (event.getType() === "m.secret.send") {
                 this.secretStorage.onSecretReceived(event);
-            } else if (event.getType() === "org.matrix.room_key.withheld") {
+            } else if (event.getType() === "m.room_key.withheld"
+                || event.getType() === "org.matrix.room_key.withheld") {
                 this.onRoomKeyWithheldEvent(event);
             } else if (event.getContent().transaction_id) {
                 this.onKeyVerificationMessage(event);