diff --git a/mp_api/client/mprester.py b/mp_api/client/mprester.py
index 0fab2eca..c7855866 100644
--- a/mp_api/client/mprester.py
+++ b/mp_api/client/mprester.py
@@ -1399,7 +1399,8 @@ def get_entries_in_chemsys(
                 )
                 n = len(unmixed)
                 entries = apply_corrections(
-                    MaterialsProjectDFTMixingScheme(),
+                    # strict structure matching, as for MP's pre-built phase diagrams
+                    MaterialsProjectDFTMixingScheme(fuzzy_matching=False),
                     unmixed,
                     description="Re-mixing GGA(+U)/r2SCAN entries",
                     log=f"Re-mixing {n:,} GGA(+U)/r2SCAN entries onto a common energy scale",
diff --git a/pyproject.toml b/pyproject.toml
index 15342ee1..562ff0bc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -40,7 +40,7 @@ classifiers = [
 ]
 
 dependencies = [
-  "pymatgen>2024.2.20",
+  "pymatgen>=2026.9.23",  # MaterialsProjectDFTMixingScheme fix for local re-mixes
   "requests>=2.23.0",
   "monty>=2024.12.10",
   "emmet-core>=0.88.0",
diff --git a/tests/client/test_mprester.py b/tests/client/test_mprester.py
index 1dbb8f04..12c25cab 100644
--- a/tests/client/test_mprester.py
+++ b/tests/client/test_mprester.py
@@ -46,6 +46,7 @@
 from mp_api.client import MPRester
 from mp_api.client.core import MPRestError, MPRestWarning
 from mp_api.client.core.settings import _DEFAULT_ENDPOINT
+from mp_api.client.routes.materials.thermo import ThermoRester
 
 try:
     from mp_api.client.contribs import ContribsClient as contribs_client
@@ -331,6 +332,18 @@ def test_get_entries_in_chemsys(self, mpr):
         ):
             mpr.get_entries_in_chemsys([Element.from_Z(1 + i).name for i in range(10)])
 
+    def test_get_entries_in_chemsys_remix_matches_served(self, mpr, monkeypatch):
+        """The client-side re-mix (used when MP has no pre-built phase diagram) matches
+        MP's pre-built phase diagram rules."""
+        served = mpr.get_entries_in_chemsys("O")
+        monkeypatch.setattr(  # force the re-mix
+            ThermoRester, "get_phase_diagram_from_chemsys", lambda *args, **kwargs: None
+        )
+        remixed = mpr.get_entries_in_chemsys("O")
+        assert {str(e.entry_id): e.energy_per_atom for e in remixed} == pytest.approx(
+            {str(e.entry_id): e.energy_per_atom for e in served}
+        )
+
     def test_get_entries_in_chemsys_mixed_hull(self, mpr):
         """Mixed GGA(+U)/r2SCAN entries must all sit on one energy scale (issue #1104).