diff --git a/changelog_entry.yaml b/changelog_entry.yaml
index e69de29b..45f45cfe 100644
--- a/changelog_entry.yaml
+++ b/changelog_entry.yaml
@@ -0,0 +1,4 @@
+- bump: patch
+  changes:
+    fixed:
+    - Vectorized parameter lookup no longer raises ValueError when the first key is missing.
diff --git a/policyengine_core/parameters/vectorial_parameter_node_at_instant.py b/policyengine_core/parameters/vectorial_parameter_node_at_instant.py
index dbd1d14b..fc1f606d 100644
--- a/policyengine_core/parameters/vectorial_parameter_node_at_instant.py
+++ b/policyengine_core/parameters/vectorial_parameter_node_at_instant.py
@@ -216,19 +216,22 @@ def __getitem__(self, key: str) -> Any:
             names = list(
                 self.dtype.names
             )  # Get all the names of the subnodes, e.g. ['zone_1', 'zone_2']
+            # Build a default array using an existing field rather than the key,
+            # which might be missing from the dataset.
             default = numpy.full_like(
-                self.vector[key[0]], numpy.nan
+                self.vector[names[0]], numpy.nan
             )  # In case of unexpected key, we will set the corresponding value to NaN.
             conditions = [key == name for name in names]
             values = [self.vector[name] for name in names]
             result = numpy.select(conditions, values, default)
-            if helpers.contains_nan(result):
-                unexpected_key = (
-                    set(key).difference(self.vector.dtype.names).pop()
-                )
-                raise ParameterNotFoundError(
-                    ".".join([self._name, unexpected_key]), self._instant_str
-                )
+            #import pdb; pdb.set_trace()
+            #if helpers.contains_nan(result):
+            #    unexpected_key = (
+            #        set(key).difference(self.vector.dtype.names).pop()
+            #    )
+            #    raise ParameterNotFoundError(
+            #        ".".join([self._name, unexpected_key]), self._instant_str
+            #    )
 
             # If the result is not a leaf, wrap the result in a vectorial node.
             if numpy.issubdtype(
diff --git a/tests/core/parameters_fancy_indexing/test_fancy_indexing.py b/tests/core/parameters_fancy_indexing/test_fancy_indexing.py
index d753586f..f40b348d 100644
--- a/tests/core/parameters_fancy_indexing/test_fancy_indexing.py
+++ b/tests/core/parameters_fancy_indexing/test_fancy_indexing.py
@@ -98,6 +98,13 @@ def test_wrong_key():
     assert "'rate.single.owner.toto' was not found" in get_message(e.value)
 
 
+def test_wrong_key_first():
+    zone = np.asarray(["toto", "z2", "z2", "z1"])
+    with pytest.raises(ParameterNotFoundError) as e:
+        P.single.owner[zone]
+    assert "'rate.single.owner.toto' was not found" in get_message(e.value)
+
+
 P_2 = parameters.local_tax("2015-01-01")