diff --git a/app/cloudfoundry_config.py b/app/cloudfoundry_config.py
index 1868924ab..293f0cd2c 100644
--- a/app/cloudfoundry_config.py
+++ b/app/cloudfoundry_config.py
@@ -43,7 +43,7 @@ def extract_notify_config(notify_config):
     os.environ['SECRET_KEY'] = notify_config['credentials']['secret_key']
     os.environ['DANGEROUS_SALT'] = notify_config['credentials']['dangerous_salt']
     os.environ['PERFORMANCE_PLATFORM_TOKEN'] = notify_config['credentials'].get('performance_platform_token', '')
-    os.environ['SMS_INBOUND_WHITELIST'] = notify_config['credentials']['allow_ip_inbound_sms']
+    os.environ['SMS_INBOUND_WHITELIST'] = json.dumps(notify_config['credentials']['allow_ip_inbound_sms'])
 
 
 def extract_notify_aws_config(aws_config):
diff --git a/app/config.py b/app/config.py
index 94950155f..1bbbb2057 100644
--- a/app/config.py
+++ b/app/config.py
@@ -1,5 +1,6 @@
 from datetime import timedelta
 import os
+import json
 
 from celery.schedules import crontab
 from kombu import Exchange, Queue
@@ -262,7 +263,7 @@ class Config(object):
 
     FREE_SMS_TIER_FRAGMENT_COUNT = 250000
 
-    SMS_INBOUND_WHITELIST = os.environ.get('SMS_INBOUND_WHITELIST', [])
+    SMS_INBOUND_WHITELIST = json.loads(os.environ.get('SMS_INBOUND_WHITELIST', '[]'))
 
 
 ######################
diff --git a/tests/app/test_cloudfoundry_config.py b/tests/app/test_cloudfoundry_config.py
index 1c1bf3271..15ff3dd55 100644
--- a/tests/app/test_cloudfoundry_config.py
+++ b/tests/app/test_cloudfoundry_config.py
@@ -204,4 +204,4 @@ def test_redis_config():
 def test_sms_inbound_config():
     extract_cloudfoundry_config()
 
-    assert os.environ['SMS_INBOUND_WHITELIST'] == ['111.111.111.111', '100.100.100.100']
+    assert os.environ['SMS_INBOUND_WHITELIST'] == json.dumps(['111.111.111.111', '100.100.100.100'])
diff --git a/tests/conftest.py b/tests/conftest.py
index bf9823331..31de496db 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -90,7 +90,13 @@ def os_environ():
     """
     # for use whenever you expect code to edit environment variables
     old_env = os.environ.copy()
-    os.environ = {}
+
+    class EnvironDict(dict):
+        def __setitem__(self, key, value):
+            assert type(value) == str
+            super().__setitem__(key, value)
+
+    os.environ = EnvironDict()
     yield
     os.environ = old_env