diff --git a/changelog.d/203.misc b/changelog.d/203.misc
new file mode 100644
index 00000000..3b7bf3bd
--- /dev/null
+++ b/changelog.d/203.misc
@@ -0,0 +1 @@
+Typescriptify MembershipCache
\ No newline at end of file
diff --git a/src/bridge.js b/src/bridge.js
index 6f33a562..9d93d789 100644
--- a/src/bridge.js
+++ b/src/bridge.js
@@ -34,7 +34,7 @@ const EventBridgeStore = require("./components/event-bridge-store");
 const MatrixUser = require("./models/users/matrix").MatrixUser;
 const MatrixRoom = require("./models/rooms/matrix").MatrixRoom;
 const { PrometheusMetrics } = require("./components/prometheusmetrics");
-const MembershipCache = require("./components/membership-cache");
+const { MembershipCache } = require("./components/membership-cache");
 const RoomLinkValidator = require("./components/room-link-validator").RoomLinkValidator;
 const RLVStatus = require("./components/room-link-validator").validationStatuses;
 const RoomUpgradeHandler = require("./components/room-upgrade-handler");
diff --git a/src/components/intent.ts b/src/components/intent.ts
index be9d258f..402b2509 100644
--- a/src/components/intent.ts
+++ b/src/components/intent.ts
@@ -20,17 +20,16 @@ import JsSdk from "matrix-js-sdk";
 const { MatrixEvent, RoomMember } = JsSdk as any;
 import ClientRequestCache from "./client-request-cache";
 import { defer } from "../utils/promiseutil";
+import { UserMembership } from "./membership-cache";
 
 
 type BridgeErrorReason = "m.event_not_handled" | "m.event_too_old"
     | "m.internal_error" | "m.foreign_network_error" | "m.event_unknown";
 
-type MembershipState = "join" | "invite" | "leave" | null; // null = unknown
-
 type BackingStore = {
-    getMembership: (roomId: string, userId: string) => MembershipState,
+    getMembership: (roomId: string, userId: string) => UserMembership,
     getPowerLevelContent: (roomId: string) => Record<string, unknown> | undefined,
-    setMembership: (roomId: string, userId: string, membership: MembershipState) => void,
+    setMembership: (roomId: string, userId: string, membership: UserMembership) => void,
     setPowerLevelContent: (roomId: string, content: Record<string, unknown>) => void,
 };
 
@@ -98,7 +97,7 @@ export class Intent {
         registered?: boolean;
     }
     // These two are only used if no opts.backingStore is provided to the constructor.
-    private readonly _membershipStates: Record<string, MembershipState> = {};
+    private readonly _membershipStates: Record<string, UserMembership> = {};
     private readonly _powerLevels: Record<string, PowerLevelContent> = {};
 
     /**
@@ -167,7 +166,7 @@ export class Intent {
                 getPowerLevelContent: (roomId: string) => {
                     return this._powerLevels[roomId];
                 },
-                setMembership: (roomId: string, userId: string, membership: MembershipState) => {
+                setMembership: (roomId: string, userId: string, membership: UserMembership) => {
                     if (userId !== this.client.credentials.userId) {
                         return;
                     }
diff --git a/src/components/membership-cache.js b/src/components/membership-cache.ts
similarity index 55%
rename from src/components/membership-cache.js
rename to src/components/membership-cache.ts
index 90a3a2c6..0e443cbf 100644
--- a/src/components/membership-cache.js
+++ b/src/components/membership-cache.ts
@@ -17,13 +17,10 @@ limitations under the License.
  * Caches membership of virtual users to rooms in memory
  * and also stores the state of whether users are registered.
  */
-class MembershipCache {
-    constructor () {
-        this._membershipMap = {
-            // room_id: { user_id: "join|invite|leave|ban|null" }   null=unknown
-        };
-        this._registeredUsers = new Set();
-    }
+export type UserMembership = "join"|"invite"|"leave"|"ban"|null;
+export class MembershipCache {
+    private membershipMap: {[roomId: string]: { [userId: string]: UserMembership }} = {};
+    private registeredUsers = new Set<string>();
 
     /**
      * Get's the *cached* state of a user's membership for a room.
@@ -32,15 +29,15 @@ class MembershipCache {
      *
      * This only caches users from the appservice.
      *
-     * @param {string}} roomId Room id to check the state of.
-     * @param {string} userId The userid to check the state of.
-     * @returns {string} The membership state of the user, e.g. "joined"
+     * @param roomId Room id to check the state of.
+     * @param userId The userid to check the state of.
+     * @returns The membership state of the user, e.g. "joined"
      */
-    getMemberEntry(roomId, userId) {
-        if (this._membershipMap[roomId] === undefined) {
+    getMemberEntry(roomId: string, userId: string): UserMembership {
+        if (this.membershipMap[roomId] === undefined) {
             return null;
         }
-        return this._membershipMap[roomId][userId];
+        return this.membershipMap[roomId][userId];
     }
 
     /**
@@ -50,27 +47,29 @@ class MembershipCache {
      * This DOES NOT set the actual membership of the room.
      *
      * This only caches users from the appservice.
-     * @param {string} roomId Room id to set the state of.
-     * @param {string} userId The userid to set the state of.
-     * @param {string} membership The membership value to set for the user
+     * @param roomId Room id to set the state of.
+     * @param userId The userid to set the state of.
+     * @param membership The membership value to set for the user
      *                       e.g joined.
      */
-    setMemberEntry(roomId, userId, membership) {
-        if (this._membershipMap[roomId] === undefined) {
-            this._membershipMap[roomId] = {};
+    setMemberEntry(roomId: string, userId: string, membership: UserMembership) {
+        if (this.membershipMap[roomId] === undefined) {
+            this.membershipMap[roomId] = {};
         }
 
         // Bans and invites do not mean the user exists.
         if (membership === "join" || membership === "leave") {
-            this._registeredUsers.add(userId);
+            this.registeredUsers.add(userId);
         }
 
-        this._membershipMap[roomId][userId] = membership;
+        this.membershipMap[roomId][userId] = membership;
     }
 
-    isUserRegistered(userId) {
-        return this._registeredUsers.has(userId);
+    /**
+     * Is a user considered registered with the homeserver.
+     * @param userId A Matrix userId
+     */
+    isUserRegistered(userId: string) {
+        return this.registeredUsers.has(userId);
     }
 }
-
-module.exports = MembershipCache;
diff --git a/src/index.ts b/src/index.ts
index 1cac6014..49bfe6d5 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -58,7 +58,7 @@ export * from "./components/prometheusmetrics";
 module.exports.PrometheusMetrics.AgeCounters = require("./components/agecounters").AgeCounters;
 
 // Caches
-module.exports.MembershipCache = require("./components/membership-cache");
+export * from "./components/membership-cache";
 
 // Logging
 module.exports.Logging = require("./components/logging");