diff --git a/packages/pybamm/src/pybamm/models/full_battery_models/base_battery_model.py b/packages/pybamm/src/pybamm/models/full_battery_models/base_battery_model.py
index 3d131c47ee..2f7d59fb5d 100644
--- a/packages/pybamm/src/pybamm/models/full_battery_models/base_battery_model.py
+++ b/packages/pybamm/src/pybamm/models/full_battery_models/base_battery_model.py
@@ -604,7 +604,7 @@ def __init__(self, extra_options):
         # phases option is provided.
         # return "1" if option not given
         phases_option = extra_options.get("particle phases", "1")
-        if phases_option == "1":
+        if phases_option in ["1", ("1", "1"), ["1", "1"]]:
             default_options["surface form"] = "false"
         else:
             default_options["surface form"] = "algebraic"
@@ -703,7 +703,7 @@ def __init__(self, extra_options):
         # then "total interfacial current density as a state" must be "true"
         if (
             options["SEI film resistance"] != "none"
-            and options["particle phases"] != "1"
+            and options["particle phases"] not in ["1", ("1", "1"), ["1", "1"]]
         ):
             options["total interfacial current density as a state"] = "true"
             # Check that extra_options did not try to provide a clashing option
@@ -849,7 +849,7 @@ def __init__(self, extra_options):
                     "current collectors in a half-cell configuration"
                 )
 
-        if options["particle phases"] not in ["1", ("1", "1")]:
+        if options["particle phases"] not in ["1", ("1", "1"), ["1", "1"]]:
             if not (
                 options["surface form"] != "false"
                 and options["particle"] == "Fickian diffusion"
diff --git a/packages/pybamm/src/pybamm/models/full_battery_models/lithium_ion/base_lithium_ion_model.py b/packages/pybamm/src/pybamm/models/full_battery_models/lithium_ion/base_lithium_ion_model.py
index 207b49115f..7a5879ebed 100644
--- a/packages/pybamm/src/pybamm/models/full_battery_models/lithium_ion/base_lithium_ion_model.py
+++ b/packages/pybamm/src/pybamm/models/full_battery_models/lithium_ion/base_lithium_ion_model.py
@@ -104,7 +104,7 @@ def default_quick_plot_variables(self):
     def calc_esoh(self):
         """Whether to include eSOH variables in the summary variables."""
         if (
-            self.options["particle phases"] not in ["1", ("1", "1")]
+            self.options["particle phases"] not in ["1", ("1", "1"), ["1", "1"]]
             or self.options["working electrode"] != "both"
         ):
             self._calc_esoh = False
diff --git a/packages/pybamm/tests/unit/test_models/test_full_battery_models/test_base_battery_model.py b/packages/pybamm/tests/unit/test_models/test_full_battery_models/test_base_battery_model.py
index cd14f8b638..9da61b396b 100644
--- a/packages/pybamm/tests/unit/test_models/test_full_battery_models/test_base_battery_model.py
+++ b/packages/pybamm/tests/unit/test_models/test_full_battery_models/test_base_battery_model.py
@@ -697,6 +697,14 @@ def test_default_options_cover_all_possible_options(self):
         for key in options.possible_options:
             assert key in options, f"Missing default for option '{key}'"
 
+    def test_explicit_single_phase_surface_form(self):
+        """Explicit single-phase specification ("1", "1") should default surface form to false."""
+        options_default = BatteryModelOptions({})
+        assert options_default["surface form"] == "false"
+
+        options_explicit_tuple = BatteryModelOptions({"particle phases": ("1", "1")})
+        assert options_explicit_tuple["surface form"] == "false"
+
 
 class TestVaasNormalization:
     """Test the centralized VAAS + surface form policy."""