diff --git a/test/test_value_array.py b/test/test_value_array.py
index 2920e5c..3757925 100644
--- a/test/test_value_array.py
+++ b/test/test_value_array.py
@@ -254,3 +254,12 @@ def test_pick_roundtrip() -> None:
             x = value * unit
             s = pickle.dumps(x)
             assert all(x == pickle.loads(s))
+
+
+class _InvalidUnit:
+    pass
+
+
+def test_invalid_unit_raises_error() -> None:
+    with pytest.raises(ValueError):
+        _ = tu.ValueArray([1, 2], _InvalidUnit())
diff --git a/tunits/core/cython/with_unit_value_array.pyx b/tunits/core/cython/with_unit_value_array.pyx
index a9dd342..4e37ef3 100644
--- a/tunits/core/cython/with_unit_value_array.pyx
+++ b/tunits/core/cython/with_unit_value_array.pyx
@@ -46,7 +46,10 @@ class ValueArray(WithUnit):
         the items.
         """
         if unit is not None:
-            unit = _try_interpret_as_with_unit(unit)
+            parsed_unit = _try_interpret_as_with_unit(unit)
+            if parsed_unit is None:
+                raise ValueError("Bad WithUnit scaling value: " + repr(unit))
+            unit = parsed_unit
 
         # If the items have units, we're supposed to extract a shared unit.
         data = np.asarray(data)