diff --git a/src/constraints.jl b/src/constraints.jl
index 90b00951e4b..e4645f0d190 100644
--- a/src/constraints.jl
+++ b/src/constraints.jl
@@ -95,6 +95,7 @@ function check_belongs_to_model(con_ref::ConstraintRef, model::AbstractModel)
     if owner_model(con_ref) !== model
         throw(ConstraintNotOwned(con_ref))
     end
+    return
 end
 
 Base.broadcastable(con_ref::ConstraintRef) = Ref(con_ref)
@@ -891,7 +892,8 @@ function constraint_object(
 end
 
 function check_belongs_to_model(con::ScalarConstraint, model)
-    return check_belongs_to_model(con.func, model)
+    check_belongs_to_model(con.func, model)
+    return
 end
 
 """
@@ -990,9 +992,8 @@ function constraint_object(
 end
 
 function check_belongs_to_model(con::VectorConstraint, model)
-    for func in con.func
-        check_belongs_to_model(func, model)
-    end
+    check_belongs_to_model(con.func, model)
+    return
 end
 
 function _moi_add_constraint(
@@ -1016,7 +1017,7 @@ function _moi_add_constraint(
     return MOI.add_constraint(model, f, s)
 end
 
-function check_belongs_to_model(f::Vector, model)
+function check_belongs_to_model(f::AbstractVector, model)
     for func in f
         check_belongs_to_model(func, model)
     end
diff --git a/src/nlp.jl b/src/nlp.jl
index 172ba5aa274..f9be0271eb7 100644
--- a/src/nlp.jl
+++ b/src/nlp.jl
@@ -218,9 +218,10 @@ struct NonlinearParameter <: AbstractJuMPScalar
     index::Int
 end
 
-function check_belongs_to_model(arg::NonlinearParameter, model::AbstractModel)
-    return arg.model === model
-end
+# A pass-through. This is needed to catch wben a parameter is used with the new
+# nonlinear API. It doesn't matter what the model is, because we're going to
+# throw an error regardless.
+check_belongs_to_model(::NonlinearParameter, ::AbstractModel) = nothing
 
 variable_ref_type(arg::NonlinearParameter) = variable_ref_type(arg.model)
 
@@ -344,9 +345,10 @@ struct NonlinearExpression <: AbstractJuMPScalar
     index::Int
 end
 
-function check_belongs_to_model(arg::NonlinearExpression, model::AbstractModel)
-    return arg.model === model
-end
+# A pass-through. This is needed to catch wben an expression is used with the
+# new nonlinear API. It doesn't matter what the model is, because we're going to
+# throw an error regardless.
+check_belongs_to_model(::NonlinearExpression, ::AbstractModel) = nothing
 
 variable_ref_type(arg::NonlinearExpression) = variable_ref_type(arg.model)
 
diff --git a/src/objective.jl b/src/objective.jl
index 6feb9a608ea..56718c94bc8 100644
--- a/src/objective.jl
+++ b/src/objective.jl
@@ -278,7 +278,10 @@ function set_objective_function(model::GenericModel, func::MOI.AbstractFunction)
     return
 end
 
-function set_objective_function(model::GenericModel, func::AbstractJuMPScalar)
+function set_objective_function(
+    model::GenericModel,
+    func::Union{AbstractJuMPScalar,AbstractVector{<:AbstractJuMPScalar}},
+)
     check_belongs_to_model(func, model)
     set_objective_function(model, moi_function(model, func))
     return
@@ -292,17 +295,6 @@ function set_objective_function(model::GenericModel{T}, func::Real) where {T}
     return
 end
 
-function set_objective_function(
-    model::GenericModel,
-    func::AbstractVector{<:AbstractJuMPScalar},
-)
-    for f in func
-        check_belongs_to_model(f, model)
-    end
-    set_objective_function(model, moi_function(model, func))
-    return
-end
-
 function set_objective_function(model::AbstractModel, func)
     return error(
         """
diff --git a/src/quad_expr.jl b/src/quad_expr.jl
index 6d9eb3aef10..3668f191292 100644
--- a/src/quad_expr.jl
+++ b/src/quad_expr.jl
@@ -702,6 +702,7 @@ function check_belongs_to_model(q::GenericQuadExpr, model::AbstractModel)
         check_belongs_to_model(variable_pair.a, model)
         check_belongs_to_model(variable_pair.b, model)
     end
+    return
 end
 
 """
diff --git a/src/variables.jl b/src/variables.jl
index ed0f0191606..658daba65ed 100644
--- a/src/variables.jl
+++ b/src/variables.jl
@@ -367,7 +367,6 @@ end
 
 """
     check_belongs_to_model(x::AbstractJuMPScalar, model::AbstractModel)
-    check_belongs_to_model(x::AbstractConstraint, model::AbstractModel)
 
 Throw [`VariableNotOwned`](@ref) if the [`owner_model`](@ref) of `x` is not
 `model`.