diff --git a/CHANGELOG.md b/CHANGELOG.md
index fa12b78cb809db953d3517d5f461dd45f27a2a26..9b27a8df31ed770979b53ea8297778fd3ab00735 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,10 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Changed
+
+- Allow lowercase server names only #11
+
 ## [1.3.0] - 2022-04-19
 
 ### Added
diff --git a/pretix_matrix_inviter/signals.py b/pretix_matrix_inviter/signals.py
index f10a800521d288ca578eb29b49cb186ab711c26f..fef84e1a7d3569048f6ca3c5e5ee7e3d6afdd323 100644
--- a/pretix_matrix_inviter/signals.py
+++ b/pretix_matrix_inviter/signals.py
@@ -46,7 +46,7 @@ def add_matrix_id_question(sender, position, **kwargs):
         "matrix_inviter_matrix_id": forms.RegexField(
             label=_("Matrix ID"),
             required=False,
-            regex="@[a-z0-9._=/-]+:.+",
+            regex="@[a-z0-9._=/-]+:[a-z0-9.-]+",
             strip=True,
             error_messages={
                 "invalid": _("Enter a Matrix ID of the form @username:homeserver.tld")