diff --git a/neurots/validator.py b/neurots/validator.py
index c760d434..0a847fab 100644
--- a/neurots/validator.py
+++ b/neurots/validator.py
@@ -38,7 +38,7 @@ class ValidationError(Exception):
 
 
 def _format_error(error):
-    return f"""In [{"->".join(error.absolute_path)}]: {error.message}"""
+    return f"""In [{"->".join([str(i) for i in error.absolute_path])}]: {error.message}"""
 
 
 def validate(instance, schema):
diff --git a/tests/test_validator.py b/tests/test_validator.py
index f5885eb5..f596c3ab 100644
--- a/tests/test_validator.py
+++ b/tests/test_validator.py
@@ -105,6 +105,14 @@ def test_unknown_root_key(self, dummy_params):
         dummy_params["unknown_param"] = 0
         tested.validate_neuron_params(dummy_params)
 
+    def test_error_in_list(self, dummy_params):
+        # Wrong element in lists should be reported correctly
+        dummy_params["grow_types"] = ["UNKNOWN TYPE"]
+        with pytest.raises(
+            tested.ValidationError, match=r"In \[grow_types->0\]: 'UNKNOWN TYPE' is not one of"
+        ):
+            tested.validate_neuron_params(dummy_params)
+
 
 def test_empty_params():
     data = {