diff --git a/tank-rust/src/dqn/feature.rs b/tank-rust/src/dqn/feature.rs
index 21e977f..6c18542 100644
--- a/tank-rust/src/dqn/feature.rs
+++ b/tank-rust/src/dqn/feature.rs
@@ -133,8 +133,8 @@ impl<'a> Info<'a> {
             normalize_angle(emeny.angle - gun_angle).tanh(),
             normalize_angle(wall.angle - gun_angle).tanh(),
         ];
-        for feature in feature.iter() {
-            assert!(!feature.is_nan());
+        for f in feature.iter() {
+            assert!(!f.is_nan(),"feature is nan: {:?}", feature);
         }
         feature
     }