diff --git a/unittests/table_json_conversion/data/error_simple_data.json b/unittests/table_json_conversion/data/error_simple_data.json
new file mode 100644
index 0000000000000000000000000000000000000000..bfea88b675ab2a6e0c1787fc401afec5c564c006
--- /dev/null
+++ b/unittests/table_json_conversion/data/error_simple_data.json
@@ -0,0 +1,11 @@
+{
+  "Training": {
+    "duration": 1.0,
+    "participants": 0.5
+  },
+  "Person": {
+    "family_name": "Auric",
+    "given_name": "Goldfinger",
+    "Organisation": "Federal Reserve"
+  }
+}
diff --git a/unittests/table_json_conversion/test_fill_xlsx.py b/unittests/table_json_conversion/test_fill_xlsx.py
index 0353eaa327ca79fd6b1cc69871f1eaee8bc4fa41..edc723d8db18e2f264811e8d4c2ac28d26d92b88 100644
--- a/unittests/table_json_conversion/test_fill_xlsx.py
+++ b/unittests/table_json_conversion/test_fill_xlsx.py
@@ -22,6 +22,8 @@
 import os
 import tempfile
 
+import jsonschema.exceptions as schema_exc
+import pytest
 from caosadvancedtools.table_json_conversion.fill_xlsx import (
     _get_path_rows, _get_row_type_column_index, fill_template)
 from openpyxl import load_workbook
@@ -76,3 +78,17 @@ def test_fill_xlsx():
                      template_file=rfp("data/multiple_refs_template.xlsx"),
                      known_good=rfp("data/multiple_refs_data.xlsx"),
                      schema=rfp("data/multiple_refs_schema.json"))
+
+
+def test_errors():
+    with pytest.raises(AssertionError) as exc:
+        fill_and_compare(json_file=rfp("data/error_simple_data.json"),
+                         template_file=rfp("data/simple_template.xlsx"),
+                         known_good=rfp("data/simple_data.xlsx"))
+    assert "Auric\nSteve" in str(exc.value)
+    with pytest.raises(schema_exc.ValidationError) as exc:
+        fill_and_compare(json_file=rfp("data/error_simple_data.json"),
+                         template_file=rfp("data/simple_template.xlsx"),
+                         known_good=rfp("data/simple_data.xlsx"),
+                         schema=rfp("data/simple_schema.json"))
+    assert exc.value.message == "0.5 is not of type 'integer'"