diff --git a/roles/custom/matrix-element-call/defaults/main.yml b/roles/custom/matrix-element-call/defaults/main.yml
index 8dd5cda0c..bd915b6c2 100644
--- a/roles/custom/matrix-element-call/defaults/main.yml
+++ b/roles/custom/matrix-element-call/defaults/main.yml
@@ -15,7 +15,7 @@ matrix_element_call_version: v0.7.2
 
 matrix_element_call_scheme: https
 
-matrix_element_call_hostname: "call.element.{{ matrix_domain }}"
+matrix_element_call_hostname: "call.{{ matrix_server_fqn_element }}"
 matrix_element_call_path_prefix: /
 
 matrix_element_call_base_path: "{{ matrix_base_data_path }}/element-call"
diff --git a/roles/custom/matrix-element-call/tasks/validate_config.yml b/roles/custom/matrix-element-call/tasks/validate_config.yml
index b27f941fc..06a625464 100644
--- a/roles/custom/matrix-element-call/tasks/validate_config.yml
+++ b/roles/custom/matrix-element-call/tasks/validate_config.yml
@@ -12,5 +12,15 @@
       You need to define a required configuration setting (`{{ item.name }}`).
   when: "item.when | bool and vars[item.name] | length == 0"
   with_items:
-    - {'name': 'matrix_element_call_base_path', when: true}
     - {'name': 'matrix_element_call_container_network', when: true}
+    - {'name': 'matrix_element_call_hostname', when: true}
+
+# Element Call appears to hardcode all paths to `/` (e.g. `/config.json`, `/assets/...`).
+# While we can properly serve the homepage and handle stripping the path prefix on our side,
+# the hardcoded URLs in the Element Call are pointing people to the wrong place, which is a problem.
+- name: Fail if Element Call path prefix is different than /
+  ansible.builtin.fail:
+    msg: >
+      Element Call with a path prefix other than '/' is not supported yet.
+      You have configured matrix_element_call_path_prefix to '{{ matrix_element_call_path_prefix }}'.
+  when: "matrix_element_call_path_prefix != '/'"