diff --git a/src/main.rs b/src/main.rs
index 2320cb3..e7388ed 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,7 +5,7 @@ use std::env;
 #[tokio::main]
 async fn main() -> Result<(), Error> {
     let token =
-        env::var("CANVAS_SECRET").expect("Canvas API key is not defined in the environment.");
+        env::var("CANVAS_SECRET").expect("Canvas API key is not defined in the environment. Please set environment variable `CANVAS_SECRET`.");
 
     // Base URL must have trailing slash or URL `.join()` will not work
     let client = CanvasClient::create(