diff --git a/src/game.rs b/src/game.rs
index ab86c53..bf37718 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -9,12 +9,15 @@ use std::str::FromStr;
 #[derive(Debug, Eq, PartialEq, Copy, Clone)]
 pub enum RoomFormat {Contiguous, CommaSeparated}
 
+#[derive(Debug)]
+pub struct InvalidRoomFormat;
+
 impl RoomFormat {
-    fn from(str: &str) -> Result<RoomFormat, &'static dyn Error> {
+    fn from(str: &str) -> Result<RoomFormat, InvalidRoomFormat> {
         match str {
             "0" => Ok(RoomFormat::Contiguous),
             "1" => Ok(RoomFormat::CommaSeparated),
-            _   => panic!(format!("Invalid room format: {}", str)),
+            _   => Err(InvalidRoomFormat),
         }
     }