diff --git a/keyserver/flow-typed/npm/@matrix-org/olm_vx.x.x.js b/keyserver/flow-typed/npm/@matrix-org/olm_vx.x.x.js
new file mode 100644
--- /dev/null
+++ b/keyserver/flow-typed/npm/@matrix-org/olm_vx.x.x.js
@@ -0,0 +1,171 @@
+// flow-typed signature: 085f002da86534cfd8cee47ffa99dd67
+// flow-typed version: <<STUB>>/@matrix-org/olm_v3.2.4/flow_v0.182.0
+
+declare module '@matrix-org/olm' {
+
+/*
+Copyright 2020 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.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+  declare export class Account {
+    constructor(): void;
+    free(): void;
+    create(): void;
+    identity_keys(): string;
+    sign(message: string | Uint8Array): string;
+    one_time_keys(): string;
+    mark_keys_as_published(): void;
+    max_number_of_one_time_keys(): number;
+    generate_one_time_keys(number_of_keys: number): void;
+    remove_one_time_keys(session: Session): void;
+    generate_fallback_key(): void;
+    fallback_key(): string;
+    unpublished_fallback_key(): string;
+    forget_old_fallback_key(): void;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): void;
+  }
+
+  declare export type EncryptResult = {
+    +type: 0 | 1, // 0: PreKey, 1: Message
+    +body: string,
+  };
+  declare export class Session {
+    constructor(): void;
+    free(): void;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): void;
+    create_outbound(
+      account: Account,
+      their_identity_key: string,
+      their_one_time_key: string,
+    ): void;
+    create_inbound(account: Account, one_time_key_message: string): void;
+    create_inbound_from(
+      account: Account,
+      identity_key: string,
+      one_time_key_message: string,
+    ): void;
+    session_id(): string;
+    has_received_message(): boolean;
+    matches_inbound(one_time_key_message: string): boolean;
+    matches_inbound_from(
+      identity_key: string,
+      one_time_key_message: string,
+    ): boolean;
+    encrypt(plaintext: string): EncryptResult;
+    decrypt(message_type: number, message: string): string;
+    describe(): string;
+  }
+
+  declare export class Utility {
+    constructor(): void;
+    free(): void;
+    sha256(input: string | Uint8Array): string;
+    ed25519_verify(
+      key: string,
+      message: string | Uint8Array,
+      signature: string,
+    ): void;
+  }
+
+  declare export type DecryptResult = {
+    +message_index: string,
+    +plaintext: string,
+  };
+
+  declare export class InboundGroupSession {
+    constructor(): void;
+    free(): void;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): void;
+    create(session_key: string): string;
+    import_session(session_key: string): string;
+    decrypt(message: string): DecryptResult;
+    session_id(): string;
+    first_known_index(): number;
+    export_session(message_index: number): string;
+  }
+
+  declare export class OutboundGroupSession {
+    constructor(): void;
+    free(): void;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): void;
+    create(): void;
+    encrypt(plaintext: string): string;
+    session_id(): string;
+    session_key(): string;
+    message_index(): number;
+  }
+
+  declare export type PkEncryptionEncryptResult = {
+    +ciphertext: string,
+    +mac: string,
+    +ephemeral: string,
+  };
+
+  declare export class PkEncryption {
+    constructor(): void;
+    free(): void;
+    set_recipient_key(key: string): void;
+    encrypt(plaintext: string): PkEncryptionEncryptResult;
+  }
+
+  declare export class PkDecryption {
+    constructor(): void;
+    free(): void;
+    init_with_private_key(key: Uint8Array): string;
+    generate_key(): string;
+    get_private_key(): Uint8Array;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): string;
+    decrypt(ephemeral_key: string, mac: string, ciphertext: string): string;
+  }
+
+  declare export class PkSigning {
+    constructor(): void;
+    free(): void;
+    init_with_seed(seed: Uint8Array): string;
+    generate_seed(): Uint8Array;
+    sign(message: string): string;
+  }
+
+  declare export class SAS {
+    constructor(): void;
+    free(): void;
+    get_pubkey(): string;
+    set_their_key(their_key: string): void;
+    generate_bytes(info: string, length: number): Uint8Array;
+    calculate_mac(input: string, info: string): string;
+    calculate_mac_fixed_base64(input: string, info: string): string;
+    calculate_mac_long_kdf(input: string, info: string): string;
+  }
+
+  declare export function init(opts?: Object): Promise<void>;
+
+  declare export function get_library_version(): [number, number, number];
+
+  declare export var PRIVATE_KEY_LENGTH: number;
+
+  declare export default {
+    init: typeof init,
+    get_library_version: typeof get_library_version,
+    PRIVATE_KEY_LENGTH: typeof PRIVATE_KEY_LENGTH,
+    Account: typeof Account,
+    Utility: typeof Utility,
+  };
+
+}
diff --git a/keyserver/src/responders/user-responders.js b/keyserver/src/responders/user-responders.js
--- a/keyserver/src/responders/user-responders.js
+++ b/keyserver/src/responders/user-responders.js
@@ -1,5 +1,6 @@
 // @flow
 
+import type { Utility as OlmUtility } from '@matrix-org/olm';
 import invariant from 'invariant';
 import { getRustAPI } from 'rust-node-addon';
 import { ErrorTypes, SiweMessage } from 'siwe';
@@ -102,8 +103,7 @@
 } from '../updaters/account-updaters.js';
 import { userSubscriptionUpdater } from '../updaters/user-subscription-updaters.js';
 import { viewerAcknowledgmentUpdater } from '../updaters/viewer-acknowledgment-updater.js';
-import { getOLMUtility } from '../utils/olm-utils.js';
-import type { OLMUtility } from '../utils/olm-utils.js';
+import { getOlmUtility } from '../utils/olm-utils.js';
 import { validateInput } from '../utils/validation-utils.js';
 
 const subscriptionUpdateRequestInputValidator = tShape({
@@ -227,7 +227,7 @@
       throw new ServerError('invalid_identity_keys_blob');
     }
 
-    const olmUtil: OLMUtility = getOLMUtility();
+    const olmUtil: OlmUtility = getOlmUtility();
     try {
       olmUtil.ed25519_verify(
         identityKeys.primaryIdentityPublicKeys.ed25519,
@@ -371,7 +371,7 @@
   if (signedIdentityKeysBlob) {
     identityKeys = JSON.parse(signedIdentityKeysBlob.payload);
 
-    const olmUtil: OLMUtility = getOLMUtility();
+    const olmUtil: OlmUtility = getOlmUtility();
     try {
       olmUtil.ed25519_verify(
         identityKeys.primaryIdentityPublicKeys.ed25519,
@@ -540,7 +540,7 @@
       throw new ServerError('invalid_identity_keys_blob');
     }
 
-    const olmUtil: OLMUtility = getOLMUtility();
+    const olmUtil: OlmUtility = getOlmUtility();
     try {
       olmUtil.ed25519_verify(
         identityKeys.primaryIdentityPublicKeys.ed25519,
diff --git a/keyserver/src/utils/olm-utils.js b/keyserver/src/utils/olm-utils.js
--- a/keyserver/src/utils/olm-utils.js
+++ b/keyserver/src/utils/olm-utils.js
@@ -1,6 +1,7 @@
 // @flow
 
 import olm from '@matrix-org/olm';
+import type { Utility as OlmUtility } from '@matrix-org/olm';
 import invariant from 'invariant';
 
 import { importJSON } from './import-json.js';
@@ -16,18 +17,8 @@
   return olmConfig;
 }
 
-export type OLMUtility = {
-  +free: () => void,
-  +sha256: (input: string | Uint8Array) => string,
-  +ed25519_verify: (
-    key: string,
-    message: string | Uint8Array,
-    signature: string,
-  ) => void,
-};
-
-let cachedOLMUtility: OLMUtility;
-function getOLMUtility(): OLMUtility {
+let cachedOLMUtility: OlmUtility;
+function getOlmUtility(): OlmUtility {
   if (cachedOLMUtility) {
     return cachedOLMUtility;
   }
@@ -35,4 +26,4 @@
   return cachedOLMUtility;
 }
 
-export { getOlmConfig, getOLMUtility };
+export { getOlmConfig, getOlmUtility };
diff --git a/web/flow-typed/npm/@matrix-org/olm_vx.x.x.js b/web/flow-typed/npm/@matrix-org/olm_vx.x.x.js
new file mode 100644
--- /dev/null
+++ b/web/flow-typed/npm/@matrix-org/olm_vx.x.x.js
@@ -0,0 +1,171 @@
+// flow-typed signature: 085f002da86534cfd8cee47ffa99dd67
+// flow-typed version: <<STUB>>/@matrix-org/olm_v3.2.4/flow_v0.182.0
+
+declare module '@matrix-org/olm' {
+
+/*
+Copyright 2020 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.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+  declare export class Account {
+    constructor(): void;
+    free(): void;
+    create(): void;
+    identity_keys(): string;
+    sign(message: string | Uint8Array): string;
+    one_time_keys(): string;
+    mark_keys_as_published(): void;
+    max_number_of_one_time_keys(): number;
+    generate_one_time_keys(number_of_keys: number): void;
+    remove_one_time_keys(session: Session): void;
+    generate_fallback_key(): void;
+    fallback_key(): string;
+    unpublished_fallback_key(): string;
+    forget_old_fallback_key(): void;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): void;
+  }
+
+  declare export type EncryptResult = {
+    +type: 0 | 1, // 0: PreKey, 1: Message
+    +body: string,
+  };
+  declare export class Session {
+    constructor(): void;
+    free(): void;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): void;
+    create_outbound(
+      account: Account,
+      their_identity_key: string,
+      their_one_time_key: string,
+    ): void;
+    create_inbound(account: Account, one_time_key_message: string): void;
+    create_inbound_from(
+      account: Account,
+      identity_key: string,
+      one_time_key_message: string,
+    ): void;
+    session_id(): string;
+    has_received_message(): boolean;
+    matches_inbound(one_time_key_message: string): boolean;
+    matches_inbound_from(
+      identity_key: string,
+      one_time_key_message: string,
+    ): boolean;
+    encrypt(plaintext: string): EncryptResult;
+    decrypt(message_type: number, message: string): string;
+    describe(): string;
+  }
+
+  declare export class Utility {
+    constructor(): void;
+    free(): void;
+    sha256(input: string | Uint8Array): string;
+    ed25519_verify(
+      key: string,
+      message: string | Uint8Array,
+      signature: string,
+    ): void;
+  }
+
+  declare export type DecryptResult = {
+    +message_index: string,
+    +plaintext: string,
+  };
+
+  declare export class InboundGroupSession {
+    constructor(): void;
+    free(): void;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): void;
+    create(session_key: string): string;
+    import_session(session_key: string): string;
+    decrypt(message: string): DecryptResult;
+    session_id(): string;
+    first_known_index(): number;
+    export_session(message_index: number): string;
+  }
+
+  declare export class OutboundGroupSession {
+    constructor(): void;
+    free(): void;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): void;
+    create(): void;
+    encrypt(plaintext: string): string;
+    session_id(): string;
+    session_key(): string;
+    message_index(): number;
+  }
+
+  declare export type PkEncryptionEncryptResult = {
+    +ciphertext: string,
+    +mac: string,
+    +ephemeral: string,
+  };
+
+  declare export class PkEncryption {
+    constructor(): void;
+    free(): void;
+    set_recipient_key(key: string): void;
+    encrypt(plaintext: string): PkEncryptionEncryptResult;
+  }
+
+  declare export class PkDecryption {
+    constructor(): void;
+    free(): void;
+    init_with_private_key(key: Uint8Array): string;
+    generate_key(): string;
+    get_private_key(): Uint8Array;
+    pickle(key: string | Uint8Array): string;
+    unpickle(key: string | Uint8Array, pickle: string): string;
+    decrypt(ephemeral_key: string, mac: string, ciphertext: string): string;
+  }
+
+  declare export class PkSigning {
+    constructor(): void;
+    free(): void;
+    init_with_seed(seed: Uint8Array): string;
+    generate_seed(): Uint8Array;
+    sign(message: string): string;
+  }
+
+  declare export class SAS {
+    constructor(): void;
+    free(): void;
+    get_pubkey(): string;
+    set_their_key(their_key: string): void;
+    generate_bytes(info: string, length: number): Uint8Array;
+    calculate_mac(input: string, info: string): string;
+    calculate_mac_fixed_base64(input: string, info: string): string;
+    calculate_mac_long_kdf(input: string, info: string): string;
+  }
+
+  declare export function init(opts?: Object): Promise<void>;
+
+  declare export function get_library_version(): [number, number, number];
+
+  declare export var PRIVATE_KEY_LENGTH: number;
+
+  declare export default {
+    init: typeof init,
+    get_library_version: typeof get_library_version,
+    PRIVATE_KEY_LENGTH: typeof PRIVATE_KEY_LENGTH,
+    Account: typeof Account,
+    Utility: typeof Utility,
+  };
+
+}