diff --git a/sentry/Dockerfile b/sentry/Dockerfile
index 34af5b2..79aa6e7 100644
--- a/sentry/Dockerfile
+++ b/sentry/Dockerfile
@@ -2,10 +2,11 @@ FROM debian:jessie
 MAINTAINER Jessica Frazelle <jess@docker.com>
 
 RUN apt-get update && apt-get install -y \
-    language-pack-en \
+    g++ \
     libpq5 \
     libpq-dev \
     libxml2-dev \
+    locales \
     postgresql-client-9.4 \
     postgresql-client-common \
     python \
@@ -29,4 +30,4 @@ ADD sentry.conf.py /sentry.conf.py
 
 ENTRYPOINT ["/usr/local/bin/sentry", "--config=/sentry.conf.py"]
 
-CMD ["upgrade"]
\ No newline at end of file
+CMD ["upgrade"]
diff --git a/sentry/sentry.conf.py b/sentry/sentry.conf.py
index 91bc2b9..b18f797 100644
--- a/sentry/sentry.conf.py
+++ b/sentry/sentry.conf.py
@@ -27,7 +27,7 @@ SENTRY_PUBLIC = False
 
 # You should configure the absolute URI to Sentry. It will attempt to guess it if you don't
 # but proxies may interfere with this.
-# SENTRY_URL_PREFIX = 'http://sentry.example.com'  # No trailing slash!
+SENTRY_URL_PREFIX = os.environ.get('SENTRY_URL_PREFIX', 'http://sentry.example.com')  # No trailing slash!
 
 SENTRY_WEB_HOST = '0.0.0.0'
 SENTRY_WEB_PORT = 9000