diff --git a/src/systems/index_cache.jl b/src/systems/index_cache.jl
index d0b687c212..ae4feec62b 100644
--- a/src/systems/index_cache.jl
+++ b/src/systems/index_cache.jl
@@ -388,8 +388,8 @@ function IndexCache(sys::AbstractSystem)
         observed_syms_to_timeseries,
         dependent_pars_to_timeseries,
         disc_buffer_templates,
-        BufferTemplate(Real, tunable_buffer_size),
-        BufferTemplate(Real, initials_buffer_size),
+        BufferTemplate(Number, tunable_buffer_size),
+        BufferTemplate(Number, initials_buffer_size),
         const_buffer_sizes,
         nonnumeric_buffer_sizes,
         symbol_to_variable
diff --git a/src/systems/problem_utils.jl b/src/systems/problem_utils.jl
index b893d9ffc6..ec72e41fe7 100644
--- a/src/systems/problem_utils.jl
+++ b/src/systems/problem_utils.jl
@@ -962,7 +962,7 @@ end
     $(TYPEDEF)
 
 A callable struct to use as the `get_updated_u0` field of `InitializationMetadata`.
-Returns the value to use for the `u0` of the problem. 
+Returns the value to use for the `u0` of the problem.
 
 # Fields
 
@@ -1160,7 +1160,7 @@ function float_type_from_varmap(varmap, floatT = Bool)
 
         if v isa AbstractArray
             floatT = promote_type(floatT, eltype(v))
-        elseif v isa Real
+        elseif v isa Number
             floatT = promote_type(floatT, typeof(v))
         end
     end
@@ -1432,7 +1432,7 @@ function check_inputmap_keys(sys, u0map, pmap)
 end
 
 const BAD_KEY_MESSAGE = """
-                        Undefined keys found in the parameter or initial condition maps. Check if symbolic variable names have been reassigned. 
+                        Undefined keys found in the parameter or initial condition maps. Check if symbolic variable names have been reassigned.
                         The following keys are invalid:
                         """
 
diff --git a/test/complex.jl b/test/complex.jl
index 69cc22c985..04be8e4dac 100644
--- a/test/complex.jl
+++ b/test/complex.jl
@@ -1,4 +1,5 @@
 using ModelingToolkit
+using OrdinaryDiffEq
 using ModelingToolkit: t_nounits as t
 using Test
 
@@ -14,3 +15,30 @@ using Test
 end
 @named mixed = ComplexModel()
 @test length(equations(mixed)) == 2
+
+@testset "Complex ODEProblem" begin
+    using ModelingToolkit: t_nounits as t, D_nounits as D
+
+    vars = @variables x(t) y(t) z(t)
+    pars = @parameters a b
+
+    eqs = [
+        D(x) ~ y - x,
+        D(y) ~ -x * z + b * abs(z),
+        D(z) ~ x * y - a
+    ]
+    @named modlorenz = System(eqs, t)
+    sys = structural_simplify(modlorenz)
+
+    ic = ModelingToolkit.get_index_cache(sys)
+    @test ic.tunable_buffer_size.type == Number
+
+    u0 = ComplexF64[-4.0, 5.0, 0.0] .+ randn(ComplexF64, 3)
+    p = ComplexF64[5.0, 0.1]
+    dict = merge(Dict(unknowns(sys) .=> u0), Dict(parameters(sys) .=> p))
+    prob = ODEProblem(sys, dict, (0.0, 1.0))
+
+    sol = solve(prob, Tsit5(), saveat = 0.1)
+
+    @test sol.u[1] isa Vector{ComplexF64}
+end