diff --git a/babybuddy/settings/render.py b/babybuddy/settings/render.py
index 848f9864..36e9c176 100644
--- a/babybuddy/settings/render.py
+++ b/babybuddy/settings/render.py
@@ -5,7 +5,7 @@ from .base import *
 RENDER_EXTERNAL_HOSTNAME = os.environ.get('RENDER_EXTERNAL_HOSTNAME')
 if RENDER_EXTERNAL_HOSTNAME:
     ALLOWED_HOSTS.append(RENDER_EXTERNAL_HOSTNAME)
-    CSRF_TRUSTED_ORIGINS = "https://" + RENDER_EXTERNAL_HOSTNAME
+    CSRF_TRUSTED_ORIGINS = "".join(["https://", RENDER_EXTERNAL_HOSTNAME])
 
 
 # Database