diff --git a/Project.toml b/Project.toml
index be8017e..27ff9e8 100644
--- a/Project.toml
+++ b/Project.toml
@@ -29,7 +29,7 @@ Aqua = "0.8"
 Dates = "1"
 DocStringExtensions = "0.8, 0.9"
 Makie = "0.24"
-ModelingToolkit = "10.3.0"
+ModelingToolkit = "10.3, 11"
 OhMyThreads = "0.8"
 StructArrays = "0.7"
 Symbolics = "6,7"
diff --git a/ext/SolarPositionModelingToolkitExt.jl b/ext/SolarPositionModelingToolkitExt.jl
index 5e446bc..25b52f4 100644
--- a/ext/SolarPositionModelingToolkitExt.jl
+++ b/ext/SolarPositionModelingToolkitExt.jl
@@ -44,7 +44,7 @@ function SolarPositionBlock(;
     refraction = NoRefraction(),
 )
     @parameters t0::DateTime = t0 [tunable = false]
-    @parameters observer::Observer = observer [tunable = false]
+    @parameters observer::typeof(observer) = observer [tunable = false]
     @parameters algorithm::SolarAlgorithm = algorithm [tunable = false]
     @parameters refraction::RefractionAlgorithm = refraction [tunable = false]
 
@@ -69,8 +69,8 @@ function SolarPositionBlock(;
         eqs,
         t,
         [azimuth, elevation, zenith],
-        #=vars=#[t0, observer, algorithm, refraction];
-        #=params=#name = name,
+        [t0, observer, algorithm, refraction];
+        #=vars=#name = name,#=params=#
     )
 end
 
diff --git a/test/Project.toml b/test/Project.toml
index c2655a2..d44d55b 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -14,7 +14,7 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 TimeZones = "f269a46b-ccf7-5d73-abea-4c690281aa53"
 
 [sources]
-SolarPosition = {path = ".."}
+SolarPosition = { path = ".." }
 
 [compat]
 Aqua = "0.8"
diff --git a/test/linting.jl b/test/linting.jl
index d664ece..a44423f 100644
--- a/test/linting.jl
+++ b/test/linting.jl
@@ -2,14 +2,14 @@ using SolarPosition
 using Test
 
 using Aqua: Aqua
-using JET: JET
 
 @testset "Aqua tests" begin
     @info "...with Aqua.jl"
     Aqua.test_all(SolarPosition)
 end
 
-if VERSION > v"1.11" # JET v0.10 requires Julia v1.12
+if VERSION > v"1.11" # JET v0.11 requires Julia v1.11+ and PrecompileTools 1.3.2+
+    using JET: JET
     @testset "JET tests" begin
         @info "...with JET.jl"
         JET.test_package(SolarPosition; target_modules = (SolarPosition,))
diff --git a/test/test-mtk.jl b/test/test-mtk.jl
index 2f2d93f..b8d839d 100644
--- a/test/test-mtk.jl
+++ b/test/test-mtk.jl
@@ -5,6 +5,7 @@ using SolarPosition: HUGHES, BENNETT, ARCHER, MICHALSKY, SG2
 using ModelingToolkit: @named, @variables, @parameters, unknowns, System, mtkcompile
 using ModelingToolkit: t_nounits as t, D_nounits as D
 using Dates: DateTime
+using TimeZones: @tz_str, astimezone
 using OrdinaryDiffEq
 using CairoMakie