diff --git a/src/batch.rs b/src/batch.rs
index dc019c3..b470b5a 100644
--- a/src/batch.rs
+++ b/src/batch.rs
@@ -260,7 +260,7 @@ impl Batch {
         event: usize,
         online: bool,
         forward: bool,
-        agents: &mut HashMap<Index, Agent>,
+        agents: &HashMap<Index, Agent>,
     ) -> Vec<Vec<Player>> {
         self.events[event]
             .teams