diff --git a/mpisppy/extensions/integer_relax_then_enforce.py b/mpisppy/extensions/integer_relax_then_enforce.py
index e9c9004d8..4be8b8ce8 100644
--- a/mpisppy/extensions/integer_relax_then_enforce.py
+++ b/mpisppy/extensions/integer_relax_then_enforce.py
@@ -28,17 +28,18 @@ def __init__(self, opt):
 
     def pre_iter0(self):
         global_toc(f"{self.__class__.__name__}: relaxing integrality constraints", self.opt.cylinder_rank == 0)
-        for s in self.opt.local_scenarios.values():
-            self.integer_relaxer.apply_to(s) 
+        self._reverse_tokens = {}
+        for sname, s in self.opt.local_scenarios.items():
+            self._reverse_tokens[sname] = self.integer_relaxer.apply_to(s)
         self._integers_relaxed = True
 
     def _unrelax_integers(self):
-        for sub in self.opt.local_scenarios.values():
+        for sname, sub in self.opt.local_scenarios.items():
             subproblem_solver = sub._solver_plugin
             vlist = None
             if is_persistent(subproblem_solver):
                 vlist = list(v for v,d in sub._relaxed_integer_vars[None].values())
-            self.integer_relaxer.apply_to(sub, options={"undo":True})
+            self.integer_relaxer.apply_to(sub, options={"reverse": self._reverse_tokens[sname]})
             if is_persistent(subproblem_solver):
                 for v in vlist:
                     subproblem_solver.update_var(v)
diff --git a/mpisppy/utils/nonant_sensitivities.py b/mpisppy/utils/nonant_sensitivities.py
index 2a06cc6c3..70d587f96 100644
--- a/mpisppy/utils/nonant_sensitivities.py
+++ b/mpisppy/utils/nonant_sensitivities.py
@@ -29,7 +29,7 @@ def nonant_sensitivies(s):
     for var in s.component_data_objects(pyo.Var):
         solution_cache[var] = var._value
     relax_int = pyo.TransformationFactory('core.relax_integer_vars')
-    relax_int.apply_to(s)
+    reverse_token = relax_int.apply_to(s)
 
     assert hasattr(s, "_relaxed_integer_vars")
 
@@ -82,7 +82,7 @@ def nonant_sensitivies(s):
         sensitivity = grad_vec_kkt_inv @ -e_x
         nonant_sensis[ndn_i] = sensitivity
 
-    relax_int.apply_to(s, options={"undo":True})
+    relax_int.apply_to(s, options={"reverse": reverse_token})
     assert not hasattr(s, "_relaxed_integer_vars")
     del s.ipopt_zL_out
     del s.ipopt_zU_out
diff --git a/setup.py b/setup.py
index bbc2497cb..2a5fef097 100644
--- a/setup.py
+++ b/setup.py
@@ -38,7 +38,7 @@
         'sortedcollections',
         'numpy',
         'scipy',
-        'pyomo>=6.4',
+        'pyomo>=6.9.3',
     ],
     extras_require={
         'doc': [