diff --git a/awslambdaric/__main__.py b/awslambdaric/__main__.py
index 1c1626b..5cbbaab 100644
--- a/awslambdaric/__main__.py
+++ b/awslambdaric/__main__.py
@@ -10,7 +10,12 @@
 
 def main(args):
     app_root = os.getcwd()
-    handler = args[1]
+
+    try:
+        handler = args[1]
+    except IndexError:
+        raise ValueError("Handler not set")
+
     lambda_runtime_api_addr = os.environ["AWS_LAMBDA_RUNTIME_API"]
 
     bootstrap.run(app_root, handler, lambda_runtime_api_addr)