diff --git a/src/problems/setcover.jl b/src/problems/setcover.jl
index 9d03b6a..fff3dc8 100644
--- a/src/problems/setcover.jl
+++ b/src/problems/setcover.jl
@@ -13,7 +13,7 @@ function __init_problems_setcover__()
     copy!(SetCoverGenerator, pyimport("miplearn.problems.setcover").SetCoverGenerator)
 end
 
-function build_setcover_model_jump(data::Any; optimizer = HiGHS.Optimizer)
+function build_setcover_model_jump(data::Any; optimizer=HiGHS.Optimizer)
     if data isa String
         data = read_pkl_gz(data)
     end
diff --git a/src/problems/tsp.jl b/src/problems/tsp.jl
index 3f86b5b..03e9d9a 100644
--- a/src/problems/tsp.jl
+++ b/src/problems/tsp.jl
@@ -12,7 +12,7 @@ function __init_problems_tsp__()
     copy!(TravelingSalesmanGenerator, pyimport("miplearn.problems.tsp").TravelingSalesmanGenerator)
 end
 
-function build_tsp_model_jump(data::Any; optimizer=HiGHS.Optimizer)
+function build_tsp_model_jump(data::Any; optimizer)
     nx = pyimport("networkx")
 
     if data isa String
@@ -65,6 +65,7 @@ function build_tsp_model_jump(data::Any; optimizer=HiGHS.Optimizer)
         model,
         lazy_enforce=lazy_enforce,
         lazy_separate=lazy_separate,
+        lp_optimizer=optimizer,
     )
 end
 
diff --git a/src/solvers/jump.jl b/src/solvers/jump.jl
index 163637e..448180e 100644
--- a/src/solvers/jump.jl
+++ b/src/solvers/jump.jl
@@ -18,15 +18,17 @@ Base.@kwdef mutable struct _JumpModelExtData
     cuts_separate::Union{Function,Nothing} = nothing
     lazy_enforce::Union{Function,Nothing} = nothing
     lazy_separate::Union{Function,Nothing} = nothing
+    lp_optimizer
 end
 
 function JuMP.copy_extension_data(
-    ::_JumpModelExtData,
+    old_ext::_JumpModelExtData,
     new_model::AbstractModel,
     ::AbstractModel,
 )
-    # Do not transfer any extension data to the new model
-    new_model.ext[:miplearn] = _JumpModelExtData()
+    new_model.ext[:miplearn] = _JumpModelExtData(
+        lp_optimizer=old_ext.lp_optimizer
+    )
 end
 
 # -----------------------------------------------------------------------------
@@ -354,8 +356,7 @@ end
 function _relax(model::JuMP.Model)
     relaxed, _ = copy_model(model)
     relax_integrality(relaxed)
-    # FIXME: Remove hardcoded optimizer
-    set_optimizer(relaxed, HiGHS.Optimizer)
+    set_optimizer(relaxed, model.ext[:miplearn].lp_optimizer)
     set_silent(relaxed)
     return relaxed
 end
@@ -395,6 +396,7 @@ function __init_solvers_jump__()
             cuts_separate::Union{Function,Nothing}=nothing,
             lazy_enforce::Union{Function,Nothing}=nothing,
             lazy_separate::Union{Function,Nothing}=nothing,
+            lp_optimizer=HiGHS.Optimizer,
         )
             self.inner = inner
             self.inner.ext[:miplearn] = _JumpModelExtData(
@@ -402,6 +404,7 @@ function __init_solvers_jump__()
                 cuts_separate=cuts_separate,
                 lazy_enforce=lazy_enforce,
                 lazy_separate=lazy_separate,
+                lp_optimizer=lp_optimizer,
             )
         end