diff --git a/src/Mjolnir.ts b/src/Mjolnir.ts
index 50034d5..32f5885 100644
--- a/src/Mjolnir.ts
+++ b/src/Mjolnir.ts
@@ -31,7 +31,7 @@ import { ReportPoller } from "./report/ReportPoller";
 import { WebAPIs } from "./webapis/WebAPIs";
 import RuleServer from "./models/RuleServer";
 import { ThrottlingQueue } from "./queues/ThrottlingQueue";
-import { IConfig } from "./config";
+import { getDefaultConfig, IConfig } from "./config";
 import PolicyList from "./models/PolicyList";
 import { ProtectedRoomsSet } from "./ProtectedRoomsSet";
 import ManagementRoomOutput from "./ManagementRoomOutput";
@@ -140,6 +140,9 @@ export class Mjolnir {
      * @returns A new Mjolnir instance that can be started without further setup.
      */
     static async setupMjolnirFromConfig(client: MatrixSendClient, matrixEmitter: MatrixEmitter, config: IConfig): Promise<Mjolnir> {
+        if (!config.autojoinOnlyIfManager && config.acceptInvitesFromSpace === getDefaultConfig().acceptInvitesFromSpace) {
+            throw new TypeError("`autojoinOnlyIfManager` has been disabled, yet no space has been provided for `acceptInvitesFromSpace`.");
+        }
         const policyLists: PolicyList[] = [];
         const joinedRooms = await client.getJoinedRooms();
 
diff --git a/src/config.ts b/src/config.ts
index 5382585..c716aa8 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -37,8 +37,13 @@ export interface IConfig {
         password: string;
     };
     dataPath: string;
-    acceptInvitesFromSpace: string;
+    /**
+     * If true, Mjolnir will only accept invites from users present in managementRoom.
+     * Otherwise a space must be provided to `acceptInvitesFromSpace`.
+     */
     autojoinOnlyIfManager: boolean;
+    /** Mjolnir will accept invites from members of this space if `autojoinOnlyIfManager` is false. */
+    acceptInvitesFromSpace: string;
     recordIgnoredInvites: boolean;
     managementRoom: string;
     verboseLogging: boolean;
@@ -127,7 +132,7 @@ const defaultConfig: IConfig = {
     },
     dataPath: "/data/storage",
     acceptInvitesFromSpace: '!noop:example.org',
-    autojoinOnlyIfManager: false,
+    autojoinOnlyIfManager: true,
     recordIgnoredInvites: false,
     managementRoom: "!noop:example.org",
     verboseLogging: false,