diff --git a/src/systems/diffeqs/abstractodesystem.jl b/src/systems/diffeqs/abstractodesystem.jl
index 3f71479fb0..277eec5c83 100644
--- a/src/systems/diffeqs/abstractodesystem.jl
+++ b/src/systems/diffeqs/abstractodesystem.jl
@@ -1439,11 +1439,17 @@ function InitializationProblem{iip, specialize}(sys::AbstractODESystem,
     if isempty(u0map) && get_initializesystem(sys) !== nothing
         isys = get_initializesystem(sys; initialization_eqs, check_units)
     elseif isempty(u0map) && get_initializesystem(sys) === nothing
-        isys = structural_simplify(
-            generate_initializesystem(sys; initialization_eqs, check_units); fully_determined)
+        isys = generate_initializesystem(sys; initialization_eqs, check_units)
+        _fully_determined = fully_determined === nothing ?
+                            length(equations(isys)) == length(unknowns(isys)) :
+                            fully_determined
+        isys = structural_simplify(isys; _fully_determined)
     else
-        isys = structural_simplify(
-            generate_initializesystem(sys; u0map, initialization_eqs, check_units); fully_determined)
+        isys = generate_initializesystem(sys; u0map, initialization_eqs, check_units)
+        _fully_determined = fully_determined === nothing ?
+                            length(equations(isys)) == length(unknowns(isys)) :
+                            fully_determined
+        isys = structural_simplify(isys; _fully_determined)
     end
 
     uninit = setdiff(unknowns(sys), [unknowns(isys); getfield.(observed(isys), :lhs)])