diff --git a/undercover/__init__.py b/undercover/__init__.py
index 8f93f33..d6ea145 100644
--- a/undercover/__init__.py
+++ b/undercover/__init__.py
@@ -1,6 +1,7 @@
 # Copyright Sage Vaillancourt 2021
 
 import os
+import sys
 
 from flask import Flask
 
@@ -12,8 +13,12 @@ def create_app(test_config=None):
     optimize_css_file()
 
     app = Flask(__name__, instance_relative_config=True)
+    secret_key = os.environ.get('UNDERCOVER_SECRET_KEY')
+    if not secret_key:
+        sys.stderr.write("WARNING: UNDERCOVER_SECRET_KEY is not defined! Application may be insecure.\n")
+        secret_key = "dev"
     app.config.from_mapping(
-        SECRET_KEY=os.environ['UNDERCOVER_SECRET_KEY'],
+        SECRET_KEY=secret_key,
         # DATABASE=os.path.join(app.instance_path, 'undercover.sqlite'),
     )