diff --git a/appservice.py b/appservice.py
index e64ff0d..151daf9 100644
--- a/appservice.py
+++ b/appservice.py
@@ -157,20 +157,20 @@ def new_message(event, user):
 
     elif event['content']['msgtype'] == 'm.image':
         text = event['content']['body'] + "\n"
-        text += app.config['MATRIX_HOST'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
+        text += app.config['MATRIX_URL'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
         embed = [raw_from_event(event)]
 
     elif event['content']['msgtype'] == 'm.video':
         text = event['content']['body'] + "\n"
-        text += app.config['MATRIX_HOST'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
+        text += app.config['MATRIX_URL'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
 
     elif event['content']['msgtype'] == 'm.audio':
         text = event['content']['body'] + "\n"
-        text += app.config['MATRIX_HOST'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
+        text += app.config['MATRIX_URL'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
 
     elif event['content']['msgtype'] == 'm.file':
         text = event['content']['body'] + "\n"
-        text += app.config['MATRIX_HOST'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
+        text += app.config['MATRIX_URL'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
 
     else:
         logger.debug('-unknown msg type- ' + event['content']['msgtype'])
@@ -208,7 +208,7 @@ def new_message(event, user):
 
 def raw_from_event(event):
 
-    url = app.config['MATRIX_HOST'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
+    url = app.config['MATRIX_URL'] + '/_matrix/media/r0/download/' + event['content']['url'][6:]
 
     if event['content']['msgtype'] == 'm.image':
         value = {'type': "photo", 'version': "1.0"}
@@ -224,7 +224,7 @@ def raw_from_event(event):
             else:
                 value['height'] = 200
             if 'thumbnail_info' in event['content']['info']:
-                value['thumbnail_url'] = app.config['MATRIX_HOST'] + '/_matrix/media/r0/download/' + event['content']['info']['thumbnail_url'][6:]
+                value['thumbnail_url'] = app.config['MATRIX_URL'] + '/_matrix/media/r0/download/' + event['content']['info']['thumbnail_url'][6:]
                 if 'w' in event['content']['info']['thumbnail_info']:
                     value['thumbnail_width'] = event['content']['info']['thumbnail_info']['w']
                 else:
diff --git a/config.yaml-sample b/config.yaml-sample
index 18716e5..d03d148 100644
--- a/config.yaml-sample
+++ b/config.yaml-sample
@@ -1,6 +1,7 @@
 SERVICE_DB: 'sqlite:///store.db'  # URL for the service database
 LISTEN_PORT: 5000  # matrix app service port to listen on
-MATRIX_HOST: 'https://localhost:8448'  # URL of the matrix server
+MATRIX_URL: 'https://<DOMAIN_NAME>' # public base URL of the matrix server
+MATRIX_HOST: 'https://localhost:8448'  # client URL of the matrix server
 MATRIX_DOMAIN: '<DOMAIN_NAME>'  # domain of the matrix server (right hand side of a matrix ID)
 MATRIX_AS_ID: '<MATRIX_ID>'  # matrix ID for the app service user
 MATRIX_AS_TOKEN: '<AUTH_TOKEN>'  # auth token for the app service user