diff --git a/Project.toml b/Project.toml
index e61ddfd47..37fb9fed8 100644
--- a/Project.toml
+++ b/Project.toml
@@ -19,7 +19,7 @@ DataInterpolations = "4"
 DiffEqBase = "6.103"
 IfElse = "0.1"
 LinearAlgebra = "1.10"
-ModelingToolkit = "8.69"
+ModelingToolkit = "9"
 OrdinaryDiffEq = "6.33"
 SafeTestsets = "0.1"
 Symbolics = "5.2"
diff --git a/docs/Project.toml b/docs/Project.toml
index 034ba981d..dffb4fce9 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -13,6 +13,6 @@ ControlSystemsBase = "1.1"
 DifferentialEquations = "7.6"
 Documenter = "1"
 IfElse = "0.1"
-ModelingToolkit = "8.67"
+ModelingToolkit = "9"
 OrdinaryDiffEq = "6.31"
 Plots = "1.36"
diff --git a/docs/src/connectors/connections.md b/docs/src/connectors/connections.md
index 83a43f2ca..3c18308bc 100644
--- a/docs/src/connectors/connections.md
+++ b/docs/src/connectors/connections.md
@@ -90,10 +90,9 @@ As can be seen, this will give a 1 equation model matching our energy dissipatio
 
 ```@example connections
 using ModelingToolkitStandardLibrary.Electrical, ModelingToolkit, DifferentialEquations
+using ModelingToolkit: t_nounits as t
 using Plots
 
-@parameters t
-
 @named resistor = Resistor(R = 1)
 @named capacitor = Capacitor(C = 1)
 @named ground = Ground()
diff --git a/docs/src/tutorials/custom_component.md b/docs/src/tutorials/custom_component.md
index 4472e839f..49a3bce6a 100644
--- a/docs/src/tutorials/custom_component.md
+++ b/docs/src/tutorials/custom_component.md
@@ -8,6 +8,7 @@ First, we need to make some imports.
 
 ```@example components
 using ModelingToolkit
+using ModelingToolkit: t_nounits as t
 using ModelingToolkitStandardLibrary.Electrical
 using ModelingToolkitStandardLibrary.Electrical: OnePort
 using OrdinaryDiffEq
@@ -35,8 +36,6 @@ end NonlinearResistor;
 this can almost be directly translated to the syntax of `ModelingToolkit`.
 
 ```@example components
-@parameters t
-
 function NonlinearResistor(; name, Ga, Gb, Ve)
     @named oneport = OnePort()
     @unpack v, i = oneport
diff --git a/docs/src/tutorials/dc_motor_pi.md b/docs/src/tutorials/dc_motor_pi.md
index 874dabb06..b682a3641 100644
--- a/docs/src/tutorials/dc_motor_pi.md
+++ b/docs/src/tutorials/dc_motor_pi.md
@@ -14,14 +14,13 @@ First, the needed packages are imported and the parameters of the model defined.
 
 ```@example dc_motor_pi
 using ModelingToolkit
+using ModelingToolkit: t_nounits as t
 using ModelingToolkitStandardLibrary.Electrical
 using ModelingToolkitStandardLibrary.Mechanical.Rotational
 using ModelingToolkitStandardLibrary.Blocks
 using OrdinaryDiffEq
 using Plots
 
-@parameters t
-
 R = 0.5 # [Ohm] armature resistance
 L = 4.5e-3 # [H] armature inductance
 k = 0.5 # [N.m/A] motor constant
diff --git a/docs/src/tutorials/input_component.md b/docs/src/tutorials/input_component.md
index 293294334..414a22eed 100644
--- a/docs/src/tutorials/input_component.md
+++ b/docs/src/tutorials/input_component.md
@@ -14,13 +14,11 @@ The `ModelingToolkitStandardLibrary.Blocks.TimeVaryingFunction` component is eas
 
 ```julia
 using ModelingToolkit
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ModelingToolkitStandardLibrary.Blocks
 using DataInterpolations
 using OrdinaryDiffEq
 
-@parameters t
-D = Differential(t)
-
 function System(f; name)
     src = TimeVaryingFunction(f)
 
diff --git a/docs/src/tutorials/rc_circuit.md b/docs/src/tutorials/rc_circuit.md
index 4004d5abd..c12ccebc1 100644
--- a/docs/src/tutorials/rc_circuit.md
+++ b/docs/src/tutorials/rc_circuit.md
@@ -29,7 +29,7 @@ rc_eqs = [connect(constant.output, source.V)
 @named rc_model = ODESystem(rc_eqs, t,
     systems = [resistor, capacitor, constant, source, ground])
 sys = structural_simplify(rc_model)
-prob = ODAEProblem(sys, Pair[], (0, 10.0))
+prob = ODEProblem(sys, Pair[], (0, 10.0))
 sol = solve(prob, Tsit5())
 plot(sol, idxs = [capacitor.v, resistor.i],
     title = "RC Circuit Demonstration",
diff --git a/docs/src/tutorials/thermal_model.md b/docs/src/tutorials/thermal_model.md
index 233e2464d..1529ec502 100644
--- a/docs/src/tutorials/thermal_model.md
+++ b/docs/src/tutorials/thermal_model.md
@@ -8,8 +8,7 @@ from dividing the total initial energy in the system by the sum of the heat capa
 
 ```@example
 using ModelingToolkitStandardLibrary.Thermal, ModelingToolkit, OrdinaryDiffEq, Plots
-
-@parameters t
+using ModelingToolkit: t_nounits as t
 
 C1 = 15
 C2 = 15
diff --git a/src/Blocks/Blocks.jl b/src/Blocks/Blocks.jl
index cc7b4cde0..35cae08fd 100644
--- a/src/Blocks/Blocks.jl
+++ b/src/Blocks/Blocks.jl
@@ -5,10 +5,7 @@ module Blocks
 using ModelingToolkit, Symbolics
 import IfElse: ifelse
 import ..@symcheck
-using ModelingToolkit: getdefault
-
-@parameters t
-D = Differential(t)
+using ModelingToolkit: getdefault, t_nounits as t, D_nounits as D
 
 export RealInput, RealOutput, SISO
 include("utils.jl")
diff --git a/src/Blocks/continuous.jl b/src/Blocks/continuous.jl
index be9bdf36c..d73edb558 100644
--- a/src/Blocks/continuous.jl
+++ b/src/Blocks/continuous.jl
@@ -620,6 +620,7 @@ See also [`StateSpace`](@ref) which handles MIMO systems, as well as [ControlSys
 
     x = collect(x)
     x_scaled = collect(x_scaled)
+    bb = collect(bb)
 
     sts = [x; x_scaled; y; u]
 
diff --git a/src/Blocks/sources.jl b/src/Blocks/sources.jl
index 8cf6a79c9..7a64f73cd 100644
--- a/src/Blocks/sources.jl
+++ b/src/Blocks/sources.jl
@@ -521,7 +521,7 @@ function Base.show(io::IO, m::MIME"text/plain", p::Parameter)
 end
 
 get_sample_time(memory::Parameter) = memory.ref
-Symbolics.@register_symbolic get_sample_time(memory)
+Symbolics.@register_symbolic get_sample_time(memory::Parameter)
 
 Base.convert(::Type{T}, x::Parameter{T}) where {T <: Real} = x.ref
 function Base.convert(::Type{<:Parameter{T}}, x::Number) where {T <: Real}
@@ -603,8 +603,9 @@ end
 function get_sampled_data(t, buffer)
     get_sampled_data(t, buffer.data, buffer.ref, buffer.circular_buffer)
 end
-Symbolics.@register_symbolic get_sampled_data(t, buffer)
-Symbolics.@register_symbolic get_sampled_data(t, buffer, dt, circular_buffer) false
+Symbolics.@register_symbolic Parameter(data::Vector, ref, circular_buffer::Bool)
+Symbolics.@register_symbolic get_sampled_data(t, buffer::Parameter)
+Symbolics.@register_symbolic get_sampled_data(t, buffer::Vector, dt, circular_buffer) false
 
 function Symbolics.derivative(::typeof(get_sampled_data), args::NTuple{2, Any}, ::Val{1})
     t = @inbounds args[1]
@@ -655,21 +656,23 @@ data input component.
         buffer,
         sample_time,
         circular_buffer = true)
+    T = eltype(buffer)
     pars = @parameters begin
-        buffer = buffer #::Vector{Real}
-        sample_time = sample_time #::Real
-        circular_buffer = circular_buffer #::Bool
+        buffer::Vector{T} = buffer #::Vector{Real}
+        sample_time::T = sample_time #::Real
+        circular_buffer::Bool = circular_buffer #::Bool
     end
+    @parameters p::Parameter{T} = Parameter(buffer, sample_time, circular_buffer)
     vars = []
     systems = @named begin
         output = RealOutput()
     end
     eqs = [
-        output.u ~ get_sampled_data(t, buffer, sample_time, circular_buffer)
+        output.u ~ get_sampled_data(t, p)
     ]
-    return ODESystem(eqs, t, vars, pars; name, systems,
+    return ODESystem(eqs, t, vars, [pars; p]; name, systems,
         defaults = [
-            output.u => get_sampled_data(0.0, buffer, sample_time, circular_buffer)
+            output.u => get_sampled_data(0.0, p)
         ])
 end
 
@@ -684,9 +687,10 @@ data input component.
 # Connectors:
   - `output`
 """
-@component function SampledData(::Val{SampledDataType.struct_based}; name, buffer)
+@component function SampledData(
+        ::Val{SampledDataType.struct_based}; name, buffer::Parameter)
     pars = @parameters begin
-        buffer = buffer #::Parameter
+        buffer::typeof(buffer) = buffer #::Parameter
     end
     vars = []
     systems = @named begin
diff --git a/src/Electrical/Electrical.jl b/src/Electrical/Electrical.jl
index 723182067..876858197 100644
--- a/src/Electrical/Electrical.jl
+++ b/src/Electrical/Electrical.jl
@@ -5,13 +5,11 @@ This library contains electrical components to build up analog circuits.
 module Electrical
 
 using ModelingToolkit, Symbolics, IfElse
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ..Thermal: HeatPort
 using ..Mechanical.Rotational: Flange, Support
 using ..Blocks: RealInput, RealOutput
 
-@parameters t
-D = Differential(t)
-
 export Pin, OnePort
 include("utils.jl")
 
diff --git a/src/Hydraulic/IsothermalCompressible/IsothermalCompressible.jl b/src/Hydraulic/IsothermalCompressible/IsothermalCompressible.jl
index 41236e1de..b58647d84 100644
--- a/src/Hydraulic/IsothermalCompressible/IsothermalCompressible.jl
+++ b/src/Hydraulic/IsothermalCompressible/IsothermalCompressible.jl
@@ -4,15 +4,13 @@ Library to model iso-thermal compressible liquid fluid flow
 module IsothermalCompressible
 
 using ModelingToolkit, Symbolics
+using ModelingToolkit: t_nounits as t, D_nounits as D
 
 using ...Blocks: RealInput, RealOutput
 using ...Mechanical.Translational: MechanicalPort, Mass
 
 using IfElse: ifelse
 
-@parameters t
-D = Differential(t)
-
 export HydraulicPort, HydraulicFluid
 include("utils.jl")
 
diff --git a/src/Magnetic/FluxTubes/FluxTubes.jl b/src/Magnetic/FluxTubes/FluxTubes.jl
index 07c7595fc..08dd00120 100644
--- a/src/Magnetic/FluxTubes/FluxTubes.jl
+++ b/src/Magnetic/FluxTubes/FluxTubes.jl
@@ -1,10 +1,8 @@
 module FluxTubes
 using ModelingToolkit
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ...Electrical: Pin
 
-@parameters t
-D = Differential(t)
-
 export PositiveMagneticPort, NegativeMagneticPort, TwoPort
 include("utils.jl")
 
diff --git a/src/Mechanical/MultiBody2D/MultiBody2D.jl b/src/Mechanical/MultiBody2D/MultiBody2D.jl
index 102434e5a..ab0e3e6c0 100644
--- a/src/Mechanical/MultiBody2D/MultiBody2D.jl
+++ b/src/Mechanical/MultiBody2D/MultiBody2D.jl
@@ -1,11 +1,9 @@
 module MultiBody2D
 
 using ModelingToolkit, Symbolics, IfElse
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ..TranslationalPosition
 
-@parameters t
-D = Differential(t)
-
 export Link
 include("components.jl")
 
diff --git a/src/Mechanical/Rotational/Rotational.jl b/src/Mechanical/Rotational/Rotational.jl
index 9a6fda31f..3e58410a1 100644
--- a/src/Mechanical/Rotational/Rotational.jl
+++ b/src/Mechanical/Rotational/Rotational.jl
@@ -4,12 +4,10 @@ Library to model 1-dimensional, rotational mechanical systems
 module Rotational
 
 using ModelingToolkit, Symbolics, IfElse
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ...Blocks: RealInput, RealOutput
 import ...@symcheck
 
-@parameters t
-D = Differential(t)
-
 export Flange, Support
 include("utils.jl")
 
diff --git a/src/Mechanical/Translational/Translational.jl b/src/Mechanical/Translational/Translational.jl
index d29231a77..4db9168ad 100644
--- a/src/Mechanical/Translational/Translational.jl
+++ b/src/Mechanical/Translational/Translational.jl
@@ -4,14 +4,11 @@ Library to model 1-dimensional, translational mechanical systems
 module Translational
 
 using ModelingToolkit, Symbolics
-using ModelingToolkit: getdefault
+using ModelingToolkit: getdefault, t_nounits as t, D_nounits as D
 
 using ModelingToolkitStandardLibrary.Blocks: RealInput, RealOutput
 using IfElse: ifelse
 
-@parameters t
-D = Differential(t)
-
 export MechanicalPort
 include("utils.jl")
 
diff --git a/src/Mechanical/TranslationalModelica/TranslationalModelica.jl b/src/Mechanical/TranslationalModelica/TranslationalModelica.jl
index 2aec491b1..0b685e429 100644
--- a/src/Mechanical/TranslationalModelica/TranslationalModelica.jl
+++ b/src/Mechanical/TranslationalModelica/TranslationalModelica.jl
@@ -4,11 +4,9 @@ Library to model 1-dimensional, translational mechanical components.
 module TranslationalModelica
 
 using ModelingToolkit, Symbolics, IfElse
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ...Blocks: RealInput, RealOutput
 
-@parameters t
-D = Differential(t)
-
 export Flange
 include("utils.jl")
 
diff --git a/src/Mechanical/TranslationalPosition/TranslationalPosition.jl b/src/Mechanical/TranslationalPosition/TranslationalPosition.jl
index 72c91835c..078f4fc50 100644
--- a/src/Mechanical/TranslationalPosition/TranslationalPosition.jl
+++ b/src/Mechanical/TranslationalPosition/TranslationalPosition.jl
@@ -4,11 +4,9 @@ Library to model 1-dimensional, translational mechanical components.
 module TranslationalPosition
 
 using ModelingToolkit, Symbolics, IfElse
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ...Blocks: RealInput, RealOutput
 
-@parameters t
-D = Differential(t)
-
 export Flange
 include("utils.jl")
 
diff --git a/src/Thermal/Thermal.jl b/src/Thermal/Thermal.jl
index d5d59fcf4..a7ad12c07 100644
--- a/src/Thermal/Thermal.jl
+++ b/src/Thermal/Thermal.jl
@@ -3,11 +3,9 @@ Library of thermal system components to model heat transfer.
 """
 module Thermal
 using ModelingToolkit, Symbolics, IfElse
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ...Blocks: RealInput, RealOutput
 
-@parameters t
-D = Differential(t)
-
 export HeatPort, Element1D
 include("utils.jl")
 
diff --git a/test/Blocks/continuous.jl b/test/Blocks/continuous.jl
index 4239583cb..994944c50 100644
--- a/test/Blocks/continuous.jl
+++ b/test/Blocks/continuous.jl
@@ -1,10 +1,9 @@
 using ModelingToolkit, ModelingToolkitStandardLibrary, OrdinaryDiffEq
 using ModelingToolkitStandardLibrary.Blocks
+using ModelingToolkit: t_nounits as t
 using OrdinaryDiffEq: ReturnCode.Success
 using Test
 
-@parameters t
-
 #=
 Testing strategy:
 The general strategy is to test systems using simple inputs where the solution
diff --git a/test/Blocks/math.jl b/test/Blocks/math.jl
index aaf7f796f..c29bba069 100644
--- a/test/Blocks/math.jl
+++ b/test/Blocks/math.jl
@@ -1,11 +1,9 @@
 using ModelingToolkitStandardLibrary.Blocks
 using ModelingToolkit, OrdinaryDiffEq, Test
 using ModelingToolkitStandardLibrary.Blocks: _clamp, _dead_zone
-using ModelingToolkit: inputs, unbound_inputs, bound_inputs
+using ModelingToolkit: inputs, unbound_inputs, bound_inputs, t_nounits as t
 using OrdinaryDiffEq: ReturnCode.Success
 
-@parameters t
-
 @testset "Gain" begin
     @named c = Constant(; k = 1)
     @named gain = Gain(; k = 1)
diff --git a/test/Blocks/nonlinear.jl b/test/Blocks/nonlinear.jl
index 4f5bd1d08..be22fc848 100644
--- a/test/Blocks/nonlinear.jl
+++ b/test/Blocks/nonlinear.jl
@@ -1,10 +1,9 @@
 using ModelingToolkit, OrdinaryDiffEq
 using ModelingToolkitStandardLibrary.Blocks
+using ModelingToolkit: t_nounits as t
 using ModelingToolkitStandardLibrary.Blocks: _clamp, _dead_zone
 using OrdinaryDiffEq: ReturnCode.Success
 
-@parameters t
-
 @testset "Limiter" begin
     @testset "Constant" begin
         @named c = Constant(; k = 1)
diff --git a/test/Blocks/sources.jl b/test/Blocks/sources.jl
index 43cc5bd7b..146fe77ff 100644
--- a/test/Blocks/sources.jl
+++ b/test/Blocks/sources.jl
@@ -1,13 +1,11 @@
 using ModelingToolkit, ModelingToolkitStandardLibrary, OrdinaryDiffEq
 using ModelingToolkitStandardLibrary.Blocks
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ModelingToolkitStandardLibrary.Blocks: smooth_sin, smooth_cos, smooth_damped_sin,
                                              smooth_square, smooth_step, smooth_ramp,
                                              smooth_triangular, triangular, square
 using OrdinaryDiffEq: ReturnCode.Success
 
-@parameters t
-D = Differential(t)
-
 @testset "Constant" begin
     @named src = Constant(k = 2)
     @named int = Integrator()
diff --git a/test/Blocks/test_analysis_points.jl b/test/Blocks/test_analysis_points.jl
index 8dae292a6..a58786de2 100644
--- a/test/Blocks/test_analysis_points.jl
+++ b/test/Blocks/test_analysis_points.jl
@@ -2,12 +2,11 @@ using Test, LinearAlgebra
 using ModelingToolkit
 using ModelingToolkitStandardLibrary.Blocks
 using OrdinaryDiffEq
-using ModelingToolkit: get_eqs, vars, @set!, get_iv
+using ModelingToolkit: get_eqs, vars, @set!, t_nounits as t
 using ControlSystemsBase
 
 @named P = FirstOrder(k = 1, T = 1)
 @named C = Gain(; k = -1)
-t = ModelingToolkit.get_iv(P)
 
 @test_logs (:warn,) (:warn,) connect(P.input, :bad_connection, C.output)
 
@@ -20,8 +19,8 @@ sys = ODESystem(eqs, t, systems = [P, C], name = :hej)
 ssys = structural_simplify(sys)
 prob = ODEProblem(ssys, [P.x => 1], (0, 10))
 sol = solve(prob, Rodas5())
-@test norm(sol[1]) >= 1
-@test norm(sol[end]) < 1e-6 # This fails without the feedback through C
+@test norm(sol.u[1]) >= 1
+@test norm(sol.u[end]) < 1e-6 # This fails without the feedback through C
 # plot(sol)
 
 matrices, _ = get_sensitivity(sys, ap)
@@ -108,7 +107,6 @@ matrices2, _ = linearize(sys, :plant_input, [P.output.u])
 @named P = FirstOrder(k = 1, T = 1)
 @named C = Gain(; k = 1)
 @named add = Blocks.Add(k2 = -1)
-t = ModelingToolkit.get_iv(P)
 
 eqs = [connect(P.output, :plant_output, add.input2)
        connect(add.output, C.input)
@@ -231,7 +229,6 @@ Si = ss(matrices...)
 @test tf(So) ≈ tf(Si)
 
 ## A simple multi-level system with loop openings
-@parameters t
 @named P_inner = FirstOrder(k = 1, T = 1)
 @named feedback = Feedback()
 @named ref = Step()
@@ -311,7 +308,6 @@ G = CS.feedback(Pss, Kss, pos_feedback = true)
 @named P = FirstOrder(k = 1, T = 1)
 @named C = Gain(; k = 1)
 @named add = Blocks.Add(k2 = -1)
-t = ModelingToolkit.get_iv(P)
 
 eqs = [connect(P.output, :plant_output, add.input2)
        connect(add.output, C.input)
diff --git a/test/Electrical/analog.jl b/test/Electrical/analog.jl
index 01f85c8cb..f19d9a923 100644
--- a/test/Electrical/analog.jl
+++ b/test/Electrical/analog.jl
@@ -1,4 +1,5 @@
 using ModelingToolkitStandardLibrary.Electrical, ModelingToolkit, OrdinaryDiffEq, Test
+using ModelingToolkit: t_nounits as t
 using ModelingToolkitStandardLibrary.Blocks: Step,
                                              Constant, Sine, Cosine, ExpSine, Ramp,
                                              Square, Triangular
@@ -7,8 +8,6 @@ using OrdinaryDiffEq: ReturnCode.Success
 
 # using Plots
 
-@parameters t
-
 @testset "sensors" begin
     @named source = Sine(offset = 1, amplitude = 10, frequency = 5)
     @named voltage = Voltage()
@@ -43,7 +42,7 @@ using OrdinaryDiffEq: ReturnCode.Success
             power_sensor
         ])
     sys = structural_simplify(model)
-    prob = ODAEProblem(sys, [], (0.0, 10.0))
+    prob = ODEProblem(sys, [], (0.0, 10.0))
     sol = solve(prob, Tsit5())
 
     # Plots.plot(sol; vars=[capacitor.v, voltage_sensor.v])
@@ -100,7 +99,7 @@ end
     @named model = ODESystem(connections, t;
         systems = [resistor, capacitor, source, voltage, ground])
     sys = structural_simplify(model)
-    prob = ODAEProblem(sys, Pair[], (0.0, 10.0))
+    prob = ODEProblem(sys, Pair[], (0.0, 10.0))
     sol = solve(prob, Tsit5())
 
     # Plots.plot(sol; vars=[source.v, capacitor.v])
@@ -124,7 +123,7 @@ end
     @named model = ODESystem(connections, t;
         systems = [resistor, inductor, source, voltage, ground])
     sys = structural_simplify(model)
-    prob = ODAEProblem(sys, Pair[], (0.0, 10.0))
+    prob = ODEProblem(sys, Pair[], (0.0, 10.0))
     sol = solve(prob, Tsit5())
 
     # Plots.plot(sol; vars=[inductor.i, inductor.i])
@@ -159,7 +158,7 @@ end
         @named model = ODESystem(connections, t;
             systems = [resistor, capacitor, source, ground, voltage])
         sys = structural_simplify(model)
-        prob = ODAEProblem(sys, Pair[], (0.0, 10.0))
+        prob = ODEProblem(sys, Pair[], (0.0, 10.0))
         sol = solve(prob, Tsit5())
         @test sol.retcode == Success
         sol = solve(prob, Rodas4())
@@ -186,7 +185,7 @@ end
     @named model = ODESystem(connections, t;
         systems = [ground, resistor, current, capacitor, source])
     sys = structural_simplify(model)
-    prob = ODAEProblem(sys, Pair[], (0.0, 10.0))
+    prob = ODEProblem(sys, Pair[], (0.0, 10.0))
     sol = solve(prob, Tsit5())
     y(x, st) = (x .> st) .* abs.(collect(x) .- st)
     @test sol.retcode == Success
@@ -296,7 +295,7 @@ _damped_sine_wave(x, f, A, st, ϕ, d) = exp((st - x) * d) * A * sin(2 * π * f *
 
         u0 = [cap.v => 0.0]
 
-        prob = ODAEProblem(vsys, u0, (0, 10.0))
+        prob = ODEProblem(vsys, u0, (0, 10.0))
         sol = solve(prob, dt = 0.1, Tsit5())
 
         @test sol.retcode == Success
@@ -362,7 +361,7 @@ end
 
         u0 = [cap.v => 0.0]
 
-        prob = ODAEProblem(isys, u0, (0, 10.0))
+        prob = ODEProblem(isys, u0, (0, 10.0))
         sol = solve(prob, dt = 0.1, Tsit5())
 
         @test sol.retcode == Success
diff --git a/test/Electrical/digital.jl b/test/Electrical/digital.jl
index 849e506da..a77862430 100644
--- a/test/Electrical/digital.jl
+++ b/test/Electrical/digital.jl
@@ -96,8 +96,6 @@ end
 
 #=
 
-@parameters t
-
 @named set1 = Set()
 @named reset1 = Reset()
 @named set2 = Set()
diff --git a/test/Hydraulic/isothermal_compressible.jl b/test/Hydraulic/isothermal_compressible.jl
index e8d71a1c8..5ee09dff7 100644
--- a/test/Hydraulic/isothermal_compressible.jl
+++ b/test/Hydraulic/isothermal_compressible.jl
@@ -1,13 +1,11 @@
 using ModelingToolkit, OrdinaryDiffEq, Test
+using ModelingToolkit: t_nounits as t, D_nounits as D
 import ModelingToolkitStandardLibrary.Hydraulic.IsothermalCompressible as IC
 import ModelingToolkitStandardLibrary.Blocks as B
 import ModelingToolkitStandardLibrary.Mechanical.Translational as T
 
 using ModelingToolkitStandardLibrary.Blocks: Parameter
 
-@parameters t
-D = Differential(t)
-
 NEWTON = NLNewton(check_div = false, always_new = true, max_iter = 100, relax = 9 // 10)
 
 @testset "Fluid Domain and Tube" begin
@@ -195,8 +193,6 @@ end
 
 @testset "Actuator System" begin
     function System(use_input, f; name)
-        @parameters t
-
         pars = @parameters begin
             p_s = 200e5
             p_r = 5e5
diff --git a/test/Magnetic/magnetic.jl b/test/Magnetic/magnetic.jl
index 8c0d1cdf8..c81439fc1 100644
--- a/test/Magnetic/magnetic.jl
+++ b/test/Magnetic/magnetic.jl
@@ -4,11 +4,10 @@ import ModelingToolkitStandardLibrary.Electrical
 import ModelingToolkitStandardLibrary.Blocks
 import ModelingToolkitStandardLibrary.Magnetic
 using ModelingToolkit, OrdinaryDiffEq, Test
+using ModelingToolkit: t_nounits as t
 using OrdinaryDiffEq: ReturnCode.Success
 # using Plots
 
-@parameters t
-
 @testset "Inductor" begin
     mu_air = 1
     l_air = 0.0001
diff --git a/test/Mechanical/multibody.jl b/test/Mechanical/multibody.jl
index 68172c57a..fde5c0cb7 100644
--- a/test/Mechanical/multibody.jl
+++ b/test/Mechanical/multibody.jl
@@ -1,12 +1,11 @@
 using ModelingToolkit
+using ModelingToolkit: t_nounits as t
 using ModelingToolkitStandardLibrary.Mechanical.MultiBody2D
 using ModelingToolkitStandardLibrary.Mechanical.TranslationalPosition
 using OrdinaryDiffEq
 # using Setfield
 using Test
 
-@parameters t
-
 @named link1 = Link(; m = 1, l = 10, I = 84, g = -9.807)
 @named link2 = Link(; m = 1, l = 10, I = 84, g = -9.807, x1_0 = 10)
 @named cart = Mass(; m = 1, s = 0)
diff --git a/test/Mechanical/rotational.jl b/test/Mechanical/rotational.jl
index 08a17c6e6..041ce379d 100644
--- a/test/Mechanical/rotational.jl
+++ b/test/Mechanical/rotational.jl
@@ -1,14 +1,12 @@
 using ModelingToolkitStandardLibrary.Mechanical.Rotational,
       ModelingToolkit, OrdinaryDiffEq,
       Test
+using ModelingToolkit: t_nounits as t, D_nounits as D
 import ModelingToolkitStandardLibrary.Blocks
 using OrdinaryDiffEq: ReturnCode.Success
 
 # using Plots
 
-@parameters t
-D = Differential(t)
-
 @testset "two inertias" begin
     @named fixed = Fixed()
     @named inertia1 = Inertia(J = 2) # this one is fixed
@@ -28,11 +26,11 @@ D = Differential(t)
     sol1 = solve(prob, Rodas4())
     @test SciMLBase.successful_retcode(sol1)
 
-    prob = ODAEProblem(sys, Pair[], (0, 10.0))
+    prob = ODEProblem(sys, Pair[], (0, 10.0))
     sol = solve(prob, Rodas4())
     @test SciMLBase.successful_retcode(sol)
 
-    prob = DAEProblem(sys, D.(states(sys)) .=> 0.0, Pair[], (0, 10.0))
+    prob = DAEProblem(sys, D.(unknowns(sys)) .=> 0.0, Pair[], (0, 10.0))
     sol = solve(prob, DFBDF())
     @test SciMLBase.successful_retcode(sol)
     @test all(sol[inertia1.w] .== 0)
@@ -86,12 +84,12 @@ end
             sine
         ])
     sys = structural_simplify(model)
-    prob = DAEProblem(sys, D.(states(sys)) .=> 0.0,
-        [D(D(inertia2.phi)) => 1.0; D.(states(model)) .=> 0.0], (0, 10.0))
+    prob = DAEProblem(sys, D.(unknowns(sys)) .=> 0.0,
+        [D(D(inertia2.phi)) => 1.0; D.(unknowns(model)) .=> 0.0], (0, 10.0))
     sol = solve(prob, DFBDF())
     @test SciMLBase.successful_retcode(sol)
 
-    prob = ODAEProblem(sys, Pair[], (0, 1.0))
+    prob = ODEProblem(sys, Pair[], (0, 1.0))
     sol = solve(prob, Rodas4())
     @test SciMLBase.successful_retcode(sol)
 
@@ -166,7 +164,7 @@ end
         ])
     @test_skip begin
         sys = structural_simplify(model) #key 7 not found
-        prob = ODAEProblem(sys, Pair[], (0, 1.0))
+        prob = ODEProblem(sys, Pair[], (0, 1.0))
         sol = solve(prob, Rodas4())
         @test SciMLBase.successful_retcode(sol)
     end
@@ -214,7 +212,7 @@ end
             angle_sensor
         ])
     sys = structural_simplify(model)
-    prob = DAEProblem(sys, D.(states(sys)) .=> 0.0, Pair[], (0, 10.0))
+    prob = DAEProblem(sys, D.(unknowns(sys)) .=> 0.0, Pair[], (0, 10.0))
 
     sol = solve(prob, DFBDF())
     @test SciMLBase.successful_retcode(sol)
@@ -261,7 +259,7 @@ end
     @test all(sol[rel_speed_sensor.w_rel.u] .== sol[speed_sensor.w.u])
     @test all(sol[torque_sensor.tau.u] .== -sol[inertia1.flange_b.tau])
 
-    prob = DAEProblem(sys, D.(states(sys)) .=> 0.0, Pair[], (0, 10.0))
+    prob = DAEProblem(sys, D.(unknowns(sys)) .=> 0.0, Pair[], (0, 10.0))
     sol = solve(prob, DFBDF())
     @test SciMLBase.successful_retcode(sol)
     @test all(sol[inertia1.w] .== 0)
diff --git a/test/Mechanical/translational.jl b/test/Mechanical/translational.jl
index ee5e93e8a..74c70e271 100644
--- a/test/Mechanical/translational.jl
+++ b/test/Mechanical/translational.jl
@@ -1,12 +1,10 @@
 using ModelingToolkit, OrdinaryDiffEq, Test
+using ModelingToolkit: t_nounits as t, D_nounits as D
 
 using ModelingToolkitStandardLibrary.Blocks
 import ModelingToolkitStandardLibrary.Mechanical.Translational as TV
 import ModelingToolkitStandardLibrary.Mechanical.TranslationalPosition as TP
 
-@parameters t
-D = Differential(t)
-
 @testset "Free" begin
     function System(; name)
         systems = @named begin
@@ -167,7 +165,8 @@ end
             connect(acc.flange, mass.flange),
             connect(acc_output, acc.output)
         ]
-        @named sys = ODESystem(eqs, t, [], []; systems = [force, source, mass, acc, acc_output])
+        @named sys = ODESystem(
+            eqs, t, [], []; systems = [force, source, mass, acc, acc_output])
         s = complete(structural_simplify(sys))
         prob = ODEProblem(s, [], (0.0, pi))
         sol = solve(prob, Tsit5())
diff --git a/test/Mechanical/translational_modelica.jl b/test/Mechanical/translational_modelica.jl
index 0a9e75377..3cb6fc3d5 100644
--- a/test/Mechanical/translational_modelica.jl
+++ b/test/Mechanical/translational_modelica.jl
@@ -1,11 +1,9 @@
 using ModelingToolkit, OrdinaryDiffEq, Test
+using ModelingToolkit: t_nounits as t, D_nounits as D
 
 using ModelingToolkitStandardLibrary.Blocks
 import ModelingToolkitStandardLibrary.Mechanical.TranslationalModelica as TP
 
-@parameters t
-D = Differential(t)
-
 @testset "spring damper mass fixed" begin
     @named damper = TP.Damper(; d = 1)
     @named spring = TP.Spring(; c = 1, s_rel0 = 1)
diff --git a/test/Thermal/demo.jl b/test/Thermal/demo.jl
index c50227156..5403681fc 100644
--- a/test/Thermal/demo.jl
+++ b/test/Thermal/demo.jl
@@ -1,9 +1,7 @@
 using ModelingToolkitStandardLibrary.Thermal, ModelingToolkit, OrdinaryDiffEq, Test
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using OrdinaryDiffEq: ReturnCode.Success
 
-@parameters t
-D = Differential(t)
-
 # Modelica example
 @testset "demo" begin
     @named mass1 = HeatCapacitor(C = 15, T = 373.15)
diff --git a/test/Thermal/thermal.jl b/test/Thermal/thermal.jl
index b6319ef5c..5cea2a01b 100644
--- a/test/Thermal/thermal.jl
+++ b/test/Thermal/thermal.jl
@@ -1,9 +1,8 @@
 using ModelingToolkitStandardLibrary.Thermal, ModelingToolkit, OrdinaryDiffEq, Test
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using ModelingToolkitStandardLibrary.Blocks: Constant, Step
 using OrdinaryDiffEq: ReturnCode.Success
 
-@parameters t
-D = Differential(t)
 #=
 # Test HeatCapacitor, TemperatureSensor, RelativeTemperatureSensor, FixedTemperature
 @testset "Heat systems" begin
diff --git a/test/chua_circuit.jl b/test/chua_circuit.jl
index 6c2a3dddc..26fa362d0 100644
--- a/test/chua_circuit.jl
+++ b/test/chua_circuit.jl
@@ -1,4 +1,5 @@
 using ModelingToolkit
+using ModelingToolkit: t_nounits as t
 using ModelingToolkitStandardLibrary.Electrical
 using ModelingToolkitStandardLibrary.Electrical: OnePort
 using OrdinaryDiffEq
@@ -6,8 +7,6 @@ using OrdinaryDiffEq: ReturnCode.Success
 using IfElse: ifelse
 
 @testset "Chua Circuit" begin
-    @parameters t
-
     @component function NonlinearResistor(; name, Ga, Gb, Ve)
         @named oneport = OnePort()
         @unpack v, i = oneport
diff --git a/test/multi_domain.jl b/test/multi_domain.jl
index 7508ec13a..7b2ef4d81 100644
--- a/test/multi_domain.jl
+++ b/test/multi_domain.jl
@@ -5,12 +5,10 @@ using ModelingToolkitStandardLibrary.Blocks
 using ModelingToolkitStandardLibrary.Thermal
 import ModelingToolkitStandardLibrary
 using ModelingToolkit, OrdinaryDiffEq, Test
+using ModelingToolkit: t_nounits as t, D_nounits as D
 using OrdinaryDiffEq: ReturnCode.Success
 # using Plots
 
-@parameters t
-D = Differential(t)
-
 @testset "DC motor" begin
     R = 0.5
     L = 4.5e-3
@@ -72,7 +70,7 @@ D = Differential(t)
     @test sol[inertia.w][idx_t]≈(dc_gain * [V_step; -tau_L_step])[2] rtol=1e-3
     @test sol[emf.i][idx_t]≈(dc_gain * [V_step; -tau_L_step])[1] rtol=1e-3
 
-    prob = DAEProblem(sys, D.(states(sys)) .=> 0.0, Pair[], (0, 6.0))
+    prob = DAEProblem(sys, D.(unknowns(sys)) .=> 0.0, Pair[], (0, 6.0))
     sol = solve(prob, DFBDF())
     @test sol.retcode == Success
     # EMF equations
@@ -161,7 +159,7 @@ end
 
     @test all(sol[inertia.w] .== sol[speed_sensor.w.u])
 
-    prob = DAEProblem(sys, D.(states(sys)) .=> 0.0, Pair[], (0, 6.0))
+    prob = DAEProblem(sys, D.(unknowns(sys)) .=> 0.0, Pair[], (0, 6.0))
     sol = solve(prob, DFBDF())
 
     @test sol.retcode == Success