diff --git a/fractal_database_matrix/models.py b/fractal_database_matrix/models.py
index e4885b6..50d67c8 100644
--- a/fractal_database_matrix/models.py
+++ b/fractal_database_matrix/models.py
@@ -28,7 +28,7 @@ async def accept_invite(self, room_id: str, target: "MatrixReplicationTarget"):
 
 
 class InMemoryMatrixCredentials(MatrixCredentials):
-    homeserver = os.environ["MATRIX_HOMESERVER_URL"]
+    homeserver: str = ""
 
     class Meta:
         proxy = True
@@ -53,6 +53,7 @@ def get_creds(self) -> Union[MatrixCredentials, InMemoryMatrixCredentials]:
         else:
             try:
                 return InMemoryMatrixCredentials(
+                    homeserver=os.environ["MATRIX_HOMESERVER_URL"],
                     matrix_id=os.environ["MATRIX_USER_ID"],
                     access_token=os.environ["MATRIX_ACCESS_TOKEN"],
                 )