diff --git a/narwhals/_dask/dataframe.py b/narwhals/_dask/dataframe.py
index d493a96313..f1ec3b6e31 100644
--- a/narwhals/_dask/dataframe.py
+++ b/narwhals/_dask/dataframe.py
@@ -372,11 +372,11 @@ def group_by(self, *by: str, drop_null_keys: bool) -> DaskLazyGroupBy:
 
         return DaskLazyGroupBy(self, list(by), drop_null_keys=drop_null_keys)
 
-    def tail(self: Self, n: int) -> Self:
+    def tail(self: Self, n: int) -> Self:  # pragma: no cover
         native_frame = self._native_frame
         n_partitions = native_frame.npartitions
 
-        if n_partitions == 1:  # pragma: no cover
+        if n_partitions == 1:
             return self._from_native_frame(self._native_frame.tail(n=n, compute=False))
         else:
             msg = "`LazyFrame.tail` is not supported for Dask backend with multiple partitions."
diff --git a/narwhals/dataframe.py b/narwhals/dataframe.py
index 93cd7d7476..385a5de050 100644
--- a/narwhals/dataframe.py
+++ b/narwhals/dataframe.py
@@ -4360,7 +4360,7 @@ def head(self, n: int = 5) -> Self:
         """
         return super().head(n)
 
-    def tail(self, n: int = 5) -> Self:
+    def tail(self, n: int = 5) -> Self:  # pragma: no cover
         r"""Get the last `n` rows.
 
         !!! warning
diff --git a/narwhals/stable/v1/__init__.py b/narwhals/stable/v1/__init__.py
index ce090982c5..f61a382649 100644
--- a/narwhals/stable/v1/__init__.py
+++ b/narwhals/stable/v1/__init__.py
@@ -934,7 +934,7 @@ def unique(self, *, maintain_order: bool | None = None) -> Self:
         Returns:
             A new expression.
         """
-        if maintain_order:
+        if maintain_order:  # pragma: no cover
             msg = "`maintain_order=True` is not supported for Expr.unique."
             raise ValueError(msg)
         if maintain_order is not None:
diff --git a/tests/expr_and_series/unique_test.py b/tests/expr_and_series/unique_test.py
index b2877c646d..7379d6ccdd 100644
--- a/tests/expr_and_series/unique_test.py
+++ b/tests/expr_and_series/unique_test.py
@@ -5,6 +5,7 @@
 import pytest
 
 import narwhals as nw
+import narwhals.stable.v1 as nw_v1
 from narwhals.exceptions import LengthChangingExprError
 from tests.utils import Constructor
 from tests.utils import ConstructorEager
@@ -26,6 +27,9 @@ def test_unique_expr(constructor: Constructor) -> None:
         expected = {"a": [1, 2]}
         assert_equal_data(result, expected)
 
+    with pytest.warns(UserWarning):
+        df.select(nw_v1.col("a").unique(maintain_order=False).sum())
+
 
 def test_unique_expr_agg(
     constructor: Constructor, request: pytest.FixtureRequest