diff --git a/packages/tom-server/src/invitation-api/services/index.ts b/packages/tom-server/src/invitation-api/services/index.ts
index 1bdf1599..5d64183c 100644
--- a/packages/tom-server/src/invitation-api/services/index.ts
+++ b/packages/tom-server/src/invitation-api/services/index.ts
@@ -159,7 +159,7 @@ export default class InvitationService implements IInvitationService {
   ): Promise<string> => {
     try {
       const response = await fetch(
-        `${this.config.matrix_server}${this.MATRIX_ROOM_PATH}`,
+        `https://${this.config.matrix_server}${this.MATRIX_ROOM_PATH}`,
         {
           method: 'POST',
           headers: {
@@ -261,7 +261,7 @@ export default class InvitationService implements IInvitationService {
     room_id: string
   ) => {
     try {
-      await fetch(`${this.config.matrix_server}/${this.MATRIX_INVITE_PATH}`, {
+      await fetch(`https://${this.config.matrix_server}/${this.MATRIX_INVITE_PATH}`, {
         method: 'POST',
         headers: {
           'Content-Type': 'application/json',
diff --git a/packages/tom-server/src/invitation-api/tests/service.test.ts b/packages/tom-server/src/invitation-api/tests/service.test.ts
index 697737bc..7e507687 100644
--- a/packages/tom-server/src/invitation-api/tests/service.test.ts
+++ b/packages/tom-server/src/invitation-api/tests/service.test.ts
@@ -28,7 +28,7 @@ describe('the Invitation API service', () => {
     dbMock as unknown as TwakeDB,
     loggerMock as unknown as TwakeLogger,
     {
-      matrix_server: 'http://localhost:789',
+      matrix_server: 'localhost',
       base_url: 'http://localhost'
     } as unknown as Config
   )