diff --git a/src/systems/diffeqs/abstractodesystem.jl b/src/systems/diffeqs/abstractodesystem.jl
index 74eb4c2809..5907ab5c09 100644
--- a/src/systems/diffeqs/abstractodesystem.jl
+++ b/src/systems/diffeqs/abstractodesystem.jl
@@ -836,6 +836,16 @@ function process_DEProblem(constructor, sys::AbstractODESystem, u0map, parammap;
             merge(parammap, clockedparammap)
         end
     end
+    if eltype(u0map) <: Number
+        u0map = unknowns(sys) .=> u0map
+    end
+    if isempty(u0map)
+        u0map = Dict()
+    end
+    u0map = todict(u0map)
+    if t !== nothing
+        u0map = merge(u0map, Dict(iv => t))
+    end
     # TODO: make it work with clocks
     # ModelingToolkit.get_tearing_state(sys) !== nothing => Requires structural_simplify first
     if sys isa ODESystem && build_initializeprob &&
@@ -843,12 +853,6 @@ function process_DEProblem(constructor, sys::AbstractODESystem, u0map, parammap;
          all(isequal(Continuous()), ci.var_domain) &&
          ModelingToolkit.get_tearing_state(sys) !== nothing) ||
         !isempty(initialization_equations(sys))) && t !== nothing
-        if eltype(u0map) <: Number
-            u0map = unknowns(sys) .=> u0map
-        end
-        if isempty(u0map)
-            u0map = Dict()
-        end
         initializeprob = ModelingToolkit.InitializationProblem(
             sys, t, u0map, parammap; guesses, warn_initialize_determined,
             initialization_eqs, eval_expression, eval_module)
@@ -871,7 +875,7 @@ function process_DEProblem(constructor, sys::AbstractODESystem, u0map, parammap;
                parammap == SciMLBase.NullParameters() && isempty(defs)
             nothing
         else
-            MTKParameters(sys, parammap, trueinit; eval_expression, eval_module)
+            MTKParameters(sys, parammap, trueinit; t0 = t, eval_expression, eval_module)
         end
     else
         u0, p, defs = get_u0_p(sys,
diff --git a/src/systems/parameter_buffer.jl b/src/systems/parameter_buffer.jl
index e491344fcd..505caba32d 100644
--- a/src/systems/parameter_buffer.jl
+++ b/src/systems/parameter_buffer.jl
@@ -15,7 +15,7 @@ end
 
 function MTKParameters(
         sys::AbstractSystem, p, u0 = Dict(); tofloat = false, use_union = false,
-        eval_expression = false, eval_module = @__MODULE__)
+        t0 = nothing, eval_expression = false, eval_module = @__MODULE__)
     ic = if has_index_cache(sys) && get_index_cache(sys) !== nothing
         get_index_cache(sys)
     else
@@ -43,6 +43,9 @@ function MTKParameters(
     defs = merge(defs, u0)
     defs = merge(Dict(eq.lhs => eq.rhs for eq in observed(sys)), defs)
     bigdefs = merge(defs, p)
+    if t0 !== nothing
+        bigdefs[get_iv(sys)] = t0
+    end
     p = Dict()
     missing_params = Set()
     pdeps = has_parameter_dependencies(sys) ? parameter_dependencies(sys) : nothing
diff --git a/test/initial_values.jl b/test/initial_values.jl
index 3a7b48901d..0b72bb51fd 100644
--- a/test/initial_values.jl
+++ b/test/initial_values.jl
@@ -91,3 +91,12 @@ eqs = [D(D(z)) ~ ones(2, 2)]
 prob = ODEProblem(sys, [], (0.0, 1.0), [A1 => 0.3])
 @test prob.ps[B1] == 0.3
 @test prob.ps[B2] == 0.7
+
+# Using indepvar in initialization
+# Issue#2799
+@variables x(t)
+@parameters p
+@mtkbuild sys = ODESystem([D(x) ~ p], t; defaults = [x => t, p => 2t])
+prob = ODEProblem(structural_simplify(sys), [], (1.0, 2.0), [])
+@test prob[x] == 1.0
+@test prob.ps[p] == 2.0