diff --git a/src/ReactiveTools.jl b/src/ReactiveTools.jl
index 3350375..eda58fa 100644
--- a/src/ReactiveTools.jl
+++ b/src/ReactiveTools.jl
@@ -1055,22 +1055,14 @@ macro onchange(location, vars, expr)
   on_vars = fieldnames_to_fields(vars, known_vars)
 
   expr, used_vars = mask(expr, known_vars)
-  do_vars = Symbol[]
 
-  for a in vars.args
-    push!(do_vars, a isa Symbol && ! in(a, used_vars) ? a : :_)
-  end
-
-  replace_reactive_vars = setdiff(known_reactive_vars, do_vars)
-  replace_non_reactive_vars = setdiff(known_non_reactive_vars, do_vars)
-
-  expr = fieldnames_to_fields(expr, known_non_reactive_vars, replace_non_reactive_vars)
-  expr = fieldnames_to_fieldcontent(expr, known_reactive_vars, replace_reactive_vars)
-  expr = unmask(expr, vcat(replace_reactive_vars, replace_non_reactive_vars))
+  expr = fieldnames_to_fields(expr, known_non_reactive_vars)
+  expr = fieldnames_to_fieldcontent(expr, known_reactive_vars)
+  expr = unmask(expr, vcat(known_reactive_vars, known_non_reactive_vars))
 
   fn = length(vars.args) == 1 ? :on : :onany
   ex = quote
-    $fn($(on_vars.args...)) do $(do_vars...)
+    $fn($(on_vars.args...)) do _...
         $(expr.args...)
     end
   end