diff --git a/src/nlp.jl b/src/nlp.jl
index 53e72f23438..64f87b75a08 100644
--- a/src/nlp.jl
+++ b/src/nlp.jl
@@ -3,6 +3,8 @@
 #  License, v. 2.0. If a copy of the MPL was not distributed with this
 #  file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
+_throw_if_legacy_error(::Any) = nothing
+
 """
     nonlinear_model(
         model::GenericModel;
@@ -209,6 +211,33 @@ struct NonlinearParameter <: AbstractJuMPScalar
     index::Int
 end
 
+function check_belongs_to_model(arg::NonlinearParameter, model::AbstractModel)
+    return arg.model === model
+end
+
+variable_ref_type(arg::NonlinearParameter) = variable_ref_type(arg.model)
+
+function _throw_if_legacy_error(p::NonlinearParameter)
+    return error(
+        """
+        Cannot mix a legacy NonlinearParameter with the new nonlinear API.
+
+        Got: $p
+
+        To update, replace calls to:
+        ```julia
+        @NLparameter(model, p == 1)
+        ```
+        with
+        ```julia
+        @variable(model, p in Parameter(1))
+        ```
+        """,
+    )
+end
+
+moi_function(p::NonlinearParameter) = _throw_if_legacy_error(p)
+
 function MOI.Nonlinear.parse_expression(
     model::MOI.Nonlinear.Model,
     expr::MOI.Nonlinear.Expression,
@@ -313,6 +342,26 @@ struct NonlinearExpression <: AbstractJuMPScalar
     index::Int
 end
 
+function check_belongs_to_model(arg::NonlinearExpression, model::AbstractModel)
+    return arg.model === model
+end
+
+variable_ref_type(arg::NonlinearExpression) = variable_ref_type(arg.model)
+
+function _throw_if_legacy_error(arg::NonlinearExpression)
+    return error(
+        """
+        Cannot mix a legacy NonlinearExpression with the new nonlinear API.
+
+        Got: $arg
+
+        To update, replace all calls to `@NLexpression` with `@expression`.
+        """,
+    )
+end
+
+moi_function(arg::NonlinearExpression) = _throw_if_legacy_error(arg)
+
 function MOI.Nonlinear.parse_expression(
     model::MOI.Nonlinear.Model,
     expr::MOI.Nonlinear.Expression,
diff --git a/src/nlp_expr.jl b/src/nlp_expr.jl
index bbbdf6c11ee..53e62fc8110 100644
--- a/src/nlp_expr.jl
+++ b/src/nlp_expr.jl
@@ -87,6 +87,7 @@ struct GenericNonlinearExpr{V<:AbstractVariableRef} <: AbstractJuMPScalar
     ) where {V<:AbstractVariableRef}
         for arg in args
             _throw_if_not_real(arg)
+            _throw_if_legacy_error(arg)
         end
         return new{V}(head, Any[a for a in args])
     end
@@ -97,6 +98,7 @@ struct GenericNonlinearExpr{V<:AbstractVariableRef} <: AbstractJuMPScalar
     ) where {V<:AbstractVariableRef}
         for arg in args
             _throw_if_not_real(arg)
+            _throw_if_legacy_error(arg)
         end
         return new{V}(head, args)
     end
diff --git a/test/test_nlp_expr.jl b/test/test_nlp_expr.jl
index 23ba19c781e..a92d624462e 100644
--- a/test/test_nlp_expr.jl
+++ b/test/test_nlp_expr.jl
@@ -371,26 +371,6 @@ function test_extension_recursion_stackoverflow(
     return
 end
 
-function test_nlparameter_interaction()
-    model = Model()
-    @variable(model, x)
-    @NLparameter(model, p == 1)
-    e = x + p
-    @test e isa GenericNonlinearExpr
-    @test string(e) == "x + ($p)"
-    return
-end
-
-function test_nlexpression_interaction()
-    model = Model()
-    @variable(model, x)
-    @NLexpression(model, expr, sin(x))
-    e = x + expr
-    @test e isa GenericNonlinearExpr
-    @test string(e) == "x + ($expr)"
-    return
-end
-
 function test_nlobjective_with_nlexpr()
     model = Model()
     @variable(model, x)
@@ -414,18 +394,6 @@ function test_nlconstraint_with_nlexpr()
     return
 end
 
-function test_jump_function_nonlinearexpr()
-    model = Model()
-    @variable(model, x)
-    @NLparameter(model, p == 1)
-    @NLexpression(model, expr1, sin(p + x))
-    @NLexpression(model, expr2, sin(expr1))
-    nlp = nonlinear_model(model)
-    @test string(jump_function(model, nlp[index(expr1)])) == "sin(($p) + $x)"
-    @test string(jump_function(model, nlp[index(expr2)])) == "sin($expr1)"
-    return
-end
-
 function test_constraint_object()
     model = Model()
     @variable(model, x)
@@ -1092,4 +1060,55 @@ function test_error_nonlinear_expr_complex_constructor()
     return
 end
 
+function test_error_legacy_expression_constructor()
+    model = Model()
+    @variable(model, x)
+    @NLexpression(model, arg, x^3)
+    err = ErrorException(
+        """
+        Cannot mix a legacy NonlinearExpression with the new nonlinear API.
+
+        Got: $arg
+
+        To update, replace all calls to `@NLexpression` with `@expression`.
+        """,
+    )
+    @test_throws err @objective(model, Min, arg)
+    @test_throws err @constraint(model, arg <= 0)
+    @test_throws err @constraint(model, arg in MOI.LessThan(0.0))
+    @test_throws err moi_function(arg)
+    @test_throws err x * arg
+    @test_throws err arg * x
+    return
+end
+
+function test_error_legacy_parameter_constructor()
+    model = Model()
+    @variable(model, x)
+    @NLparameter(model, p == 1)
+    err = ErrorException(
+        """
+        Cannot mix a legacy NonlinearParameter with the new nonlinear API.
+
+        Got: $p
+
+        To update, replace calls to:
+        ```julia
+        @NLparameter(model, p == 1)
+        ```
+        with
+        ```julia
+        @variable(model, p in Parameter(1))
+        ```
+        """,
+    )
+    @test_throws err @objective(model, Min, p)
+    @test_throws err @constraint(model, p <= 0)
+    @test_throws err @constraint(model, p in MOI.LessThan(0.0))
+    @test_throws err moi_function(p)
+    @test_throws err x * p
+    @test_throws err p * x
+    return
+end
+
 end  # module