diff --git a/src/book/summary.rs b/src/book/summary.rs
index 5c7bad38..d6daf2a1 100644
--- a/src/book/summary.rs
+++ b/src/book/summary.rs
@@ -747,6 +747,8 @@ mod tests {
         let got = parser.parse_affix(false);
 
         assert!(got.is_err());
+        let error_message = got.err().unwrap().to_string();
+        assert_eq!(error_message, "failed to parse SUMMARY.md line 2, column 1: Suffix chapters cannot be followed by a list");
     }
 
     #[test]