diff --git a/python_tests/filter_fixtures.py b/python_tests/filter_fixtures.py
index 6416212..cd41efa 100644
--- a/python_tests/filter_fixtures.py
+++ b/python_tests/filter_fixtures.py
@@ -115,7 +115,7 @@ def timeseries_corpus(sync_client, datasets, prefix, token):
         ),
         "pump_x1": dict(
             external_id=f"{prefix}_ts_pumpX1", name=f"Pump Beta {token}",
-            unit="celsius", unit_external_id="temperature_c", value_type="float",
+            unit="celsius", unit_external_id="temperature_deg_c", value_type="float",
             data_set_id=child.id,
             metadata={f"tsk_{token}": "beta", f"tsshared_{token}": "yes"},
         ),
diff --git a/python_tests/test_filter_timeseries.py b/python_tests/test_filter_timeseries.py
index 4495745..894f26f 100644
--- a/python_tests/test_filter_timeseries.py
+++ b/python_tests/test_filter_timeseries.py
@@ -211,7 +211,7 @@ def test_unit_external_ids_are_a_pattern_list(flt, timeseries_corpus):
     assert flt(unit_external_id=["pressure_bar"]) == {
         timeseries_corpus["pump_1"].external_id, timeseries_corpus["valve"].external_id
     }
-    assert flt(unit_external_id=["pressure_*", "temperature_c"]) == {
+    assert flt(unit_external_id=["pressure_*", "temperature_deg_c"]) == {
         ts.external_id for ts in timeseries_corpus.values()
     }
 
diff --git a/python_tests/test_timeseries_crud.py b/python_tests/test_timeseries_crud.py
index e651b71..964e2f1 100644
--- a/python_tests/test_timeseries_crud.py
+++ b/python_tests/test_timeseries_crud.py
@@ -46,7 +46,7 @@ def _refetch(sync_client, ts):
         {"value_type": "float", "metadata": {}},
         {"value_type": "float", "metadata": {"empty_value": ""}},
         {"value_type": "float", "description": "a described series"},
-        {"value_type": "float", "unit": "m/s", "unit_external_id": "ext.unit.id"},
+        {"value_type": "float", "unit": "bar", "unit_external_id": "pressure_bar"},
         {"value_type": "float", "name": "Unicode ✓ 日本語 name"},
         {"value_type": "float", "source": "sap_pi"},
     ],
@@ -144,9 +144,7 @@ def test_delete_by_external_id_string(sync_client):
         ("unit", "Updated Unit", "unit"),
         ("description", "Updated Description", "description"),
         ("source", "updated_source", "source"),
-        # unit_external_id is sanitised server-side (dots -> underscores), so the
-        # value here is already in canonical form to keep the assertion exact.
-        ("unit_external_id", "updated_unit_ext", "unit_external_id"),
+        ("unit_external_id", "pressure_bar", "unit_external_id"),
     ],
 )
 def test_update_scalar_str_set_value(sync_client, make_ts, field, new_value, attr):
@@ -154,7 +152,7 @@ def test_update_scalar_str_set_value(sync_client, make_ts, field, new_value, att
         name="Original",
         description="original description",
         unit="a.u",
-        unit_external_id="orig_unit_ext",
+        unit_external_id="temperature_deg_c",
         source="original_source",
     )
 
@@ -202,7 +200,7 @@ def test_update_scalar_str_set_null(sync_client, make_ts, field, attr):
     ts = make_ts(
         description="please clear me",
         unit="a.u",
-        unit_external_id="clear.this.ext",
+        unit_external_id="temperature_deg_c",
         source="please_clear_me",
     )
 
diff --git a/src/resources/tests.rs b/src/resources/tests.rs
index 45be52d..a103777 100644
--- a/src/resources/tests.rs
+++ b/src/resources/tests.rs
@@ -809,7 +809,7 @@ async fn graph_projection_is_one_to_one_and_typed() -> Result<(), Box<dyn std::e
 
     let mut ts = TimeSeries::new(&ts_ext, "GP TS");
     ts.set_unit("deg C")
-        .set_unit_external_id("celsius")
+        .set_unit_external_id("temperature_deg_c")
         .set_description("ts description")
         .set_data_set_id(ds_id)
         .set_metadata(hashmap! {"tk".to_string() => "tv".to_string()});