diff --git a/py-polars/polars/datatypes.py b/py-polars/polars/datatypes.py
index e40adfabfc24..977e40bc2339 100644
--- a/py-polars/polars/datatypes.py
+++ b/py-polars/polars/datatypes.py
@@ -801,5 +801,10 @@ def maybe_cast(
 
     py_type = dtype_to_py_type(dtype)
     if not isinstance(el, py_type):
-        el = py_type(el)  # type: ignore[call-arg]
+        try:
+            el = py_type(el)  # type: ignore[call-arg]
+        except Exception:
+            raise ValueError(
+                f"Cannot convert Python type {type(el)} to {dtype}"
+            ) from None
     return el
diff --git a/py-polars/tests/unit/test_series.py b/py-polars/tests/unit/test_series.py
index 36e2ada41ea9..84a511bf90ab 100644
--- a/py-polars/tests/unit/test_series.py
+++ b/py-polars/tests/unit/test_series.py
@@ -340,7 +340,7 @@ def test_arithmetic(s: pl.Series) -> None:
         2 % a
     with pytest.raises(ValueError):
         2**a
-    with pytest.raises(TypeError):  # https://github.com/pola-rs/polars/issues/6617
+    with pytest.raises(ValueError):
         +a
     a = pl.Series("a", [""])
     with pytest.raises(ValueError):