diff --git a/src/inputoutput.jl b/src/inputoutput.jl
index 5f9420ff3a..28b60b13dc 100644
--- a/src/inputoutput.jl
+++ b/src/inputoutput.jl
@@ -218,7 +218,7 @@ function generate_control_function(sys::AbstractODESystem, inputs = unbound_inpu
         inputs = setdiff(inputs, disturbance_inputs)
         # ps = [ps; disturbance_inputs]
     end
-    inputs = map(x -> time_varying_as_func(value(x), sys), inputs)
+    inputs = map(value, inputs)
     disturbance_inputs = unwrap.(disturbance_inputs)
 
     eqs = [eq for eq in full_equations(sys)]
diff --git a/src/systems/abstractsystem.jl b/src/systems/abstractsystem.jl
index 67bcbc88c0..35ea90d6b7 100644
--- a/src/systems/abstractsystem.jl
+++ b/src/systems/abstractsystem.jl
@@ -1822,20 +1822,6 @@ function isaffine(sys::AbstractSystem)
     all(isaffine(r, unknowns(sys)) for r in rhs)
 end
 
-function time_varying_as_func(x, sys::AbstractTimeDependentSystem)
-    # if something is not x(t) (the current unknown)
-    # but is `x(t-1)` or something like that, pass in `x` as a callable function rather
-    # than pass in a value in place of x(t).
-    #
-    # This is done by just making `x` the argument of the function.
-    if iscall(x) &&
-       issym(operation(x)) &&
-       !(length(arguments(x)) == 1 && isequal(arguments(x)[1], get_iv(sys)))
-        return operation(x)
-    end
-    return x
-end
-
 """
 $(SIGNATURES)
 
diff --git a/src/systems/callbacks.jl b/src/systems/callbacks.jl
index 07809bf611..7d542d9bd0 100644
--- a/src/systems/callbacks.jl
+++ b/src/systems/callbacks.jl
@@ -598,8 +598,8 @@ Notes
 """
 function compile_condition(cb::SymbolicDiscreteCallback, sys, dvs, ps;
         expression = Val{true}, eval_expression = false, eval_module = @__MODULE__, kwargs...)
-    u = map(x -> time_varying_as_func(value(x), sys), dvs)
-    p = map.(x -> time_varying_as_func(value(x), sys), reorder_parameters(sys, ps))
+    u = map(value, dvs)
+    p = map.(value, reorder_parameters(sys, ps))
     t = get_iv(sys)
     condit = condition(cb)
     cs = collect_constants(condit)
@@ -685,8 +685,8 @@ function compile_affect(eqs::Vector{Equation}, cb, sys, dvs, ps; outputidxs = no
         _ps = ps
         ps = reorder_parameters(sys, ps)
         if checkvars
-            u = map(x -> time_varying_as_func(value(x), sys), dvs)
-            p = map.(x -> time_varying_as_func(value(x), sys), ps)
+            u = map(value, dvs)
+            p = map.(value, ps)
         else
             u = dvs
             p = ps
diff --git a/src/systems/codegen_utils.jl b/src/systems/codegen_utils.jl
index a3fe53b95d..bedfdbcc37 100644
--- a/src/systems/codegen_utils.jl
+++ b/src/systems/codegen_utils.jl
@@ -179,17 +179,6 @@ function build_function_wrapper(sys::AbstractSystem, expr, args...; p_start = 2,
 
     args = ntuple(Val(length(args))) do i
         arg = args[i]
-        # for time-dependent systems, all arguments are passed through `time_varying_as_func`
-        # TODO: This is legacy behavior and a candidate for removal in v10 since we have callable
-        # parameters now.
-        if is_time_dependent(sys)
-            arg = if symbolic_type(arg) == NotSymbolic()
-                arg isa AbstractArray ?
-                map(x -> time_varying_as_func(unwrap(x), sys), arg) : arg
-            else
-                time_varying_as_func(unwrap(arg), sys)
-            end
-        end
         # Make sure to use the proper names for arguments
         if symbolic_type(arg) == NotSymbolic() && arg isa AbstractArray
             DestructuredArgs(arg, generated_argument_name(i); create_bindings)
diff --git a/test/odesystem.jl b/test/odesystem.jl
index a45ed99f35..5710b50ed6 100644
--- a/test/odesystem.jl
+++ b/test/odesystem.jl
@@ -135,19 +135,7 @@ du = zeros(3)
 tgrad_iip(du, u, p, t)
 @test du == [0.0, -u[2], 0.0]
 
-@parameters σ′(t - 1)
-eqs = [D(x) ~ σ′ * (y - x),
-    D(y) ~ x * (ρ - z) - y,
-    D(z) ~ x * y - β * z * κ]
-@named de = ODESystem(eqs, t)
-test_diffeq_inference("global iv-varying", de, t, (x, y, z), (σ′, ρ, β))
-
-f = generate_function(de, [x, y, z], [σ′, ρ, β], expression = Val{false})[2]
-du = [0.0, 0.0, 0.0]
-f(du, [1.0, 2.0, 3.0], [x -> x + 7, 2, 3], 5.0)
-@test du ≈ [11, -3, -7]
-
-@parameters σ(..)
+@parameters (σ::Function)(..)
 eqs = [D(x) ~ σ(t - 1) * (y - x),
     D(y) ~ x * (ρ - z) - y,
     D(z) ~ x * y - β * z * κ]