diff --git a/src/forward.jl b/src/forward.jl
index 12d6719..7db6ce7 100644
--- a/src/forward.jl
+++ b/src/forward.jl
@@ -126,7 +126,8 @@ function (kfn::kfn_1)(input::AbstractArray)
                 kfn.on_recSignal,
                 kfn.on_subscription,
                 )
-    
+    # get on_zt4d to on_zt
+    kfn.on_zt .= reduce(max, kfn.on_zt4d, dims=(1,2))
     logit = reshape(kfn.on_zt, (size(input, 1), :))
 
 #     error("DEBUG -> kfn forward")