diff --git a/src/Utilities/mockoptimizer.jl b/src/Utilities/mockoptimizer.jl
index 5f73ba77fe..b3069707bb 100644
--- a/src/Utilities/mockoptimizer.jl
+++ b/src/Utilities/mockoptimizer.jl
@@ -535,6 +535,11 @@ end
 # TODO: transform
 
 MOI.supports_constraint(mock::MockOptimizer, F::Type{<:MOI.AbstractFunction}, S::Type{<:MOI.AbstractSet}) = MOI.supports_constraint(mock.inner_model, F, S)
+MOI.supports_add_constrained_variable(mock::MockOptimizer, S::Type{<:MOI.AbstractScalarSet}) = MOI.supports_add_constrained_variable(mock.inner_model, S)
+MOI.supports_add_constrained_variables(mock::MockOptimizer, S::Type{<:MOI.AbstractVectorSet}) = MOI.supports_add_constrained_variables(mock.inner_model, S)
+# Add this method to avoid ambiguity
+MOI.supports_add_constrained_variables(mock::MockOptimizer, ::Type{MOI.Reals}) = MOI.supports_add_constrained_variables(mock.inner_model, MOI.Reals)
+
 function MOI.copy_to(mock::MockOptimizer, src::MOI.ModelLike; kws...)
     automatic_copy_to(mock, src; kws...)
 end
diff --git a/test/Utilities/mockoptimizer.jl b/test/Utilities/mockoptimizer.jl
index dd983cc5fd..9bf4371b4b 100644
--- a/test/Utilities/mockoptimizer.jl
+++ b/test/Utilities/mockoptimizer.jl
@@ -19,6 +19,22 @@ end
     MOIT.nametest(MOIU.MockOptimizer(MOIU.Model{Float64}()))
 end
 
+struct NoFreeModel <: MOI.ModelLike end
+MOI.supports_add_constrained_variables(::NoFreeModel, ::Type{MOI.Reals}) = false
+
+@testset "supports_add_constrained_variable" begin
+    optimizer = MOIU.MockOptimizer(MOIU.Model{Float64}())
+    @test MOI.supports_add_constrained_variable(optimizer, MOI.GreaterThan{Float64})
+    @test !MOI.supports_add_constrained_variable(optimizer, MOIT.UnknownScalarSet{Float64})
+    @test MOI.supports_add_constrained_variables(optimizer, MOI.Nonnegatives)
+    @test !MOI.supports_add_constrained_variables(optimizer, MOIT.UnknownVectorSet)
+
+    nofree_optimizer = MOIU.MockOptimizer(NoFreeModel())
+    @test !MOI.supports_add_constrained_variable(nofree_optimizer, MOI.GreaterThan{Float64})
+    @test !MOI.supports_add_constrained_variables(nofree_optimizer, MOI.Nonnegatives)
+    @test !MOI.supports_add_constrained_variables(nofree_optimizer, MOI.Reals)
+end
+
 @testset "Optimizer attributes" begin
     optimizer = MOIU.MockOptimizer(MOIU.Model{Float64}())
     @test MOI.supports(optimizer, MOIU.MockModelAttribute())