diff --git a/src/position.rs b/src/position.rs
index 1b946c9..f34d5de 100644
--- a/src/position.rs
+++ b/src/position.rs
@@ -9,6 +9,11 @@ impl From<String> for Position {
         // e.g. "2,5"
         let xy: Vec<&str> = string.split(',').collect();
         let x = xy[0].parse().unwrap();
+
+        if xy.len() < 2 {
+            panic!("Bad position : {}", string);
+        }
+
         let y = xy[1].parse().unwrap();
 
         Position { x, y }