diff --git a/unittests/table_json_conversion/data/simple_data_ascii_chars.json b/unittests/table_json_conversion/data/simple_data_ascii_chars.json
new file mode 100644
index 0000000000000000000000000000000000000000..049b7203ce178885e436e2b2157cb70a6846fd74
--- /dev/null
+++ b/unittests/table_json_conversion/data/simple_data_ascii_chars.json
@@ -0,0 +1,18 @@
+{
+  "Training": {
+    "date": "2023-01-01",
+    "url": "char: \u0001\u0002\u0003\u0004\u0005\u0006\u0007\u0008\u0009",
+    "subjects": [
+      "\u000a\u000b\u000c\u000d\u000e\u000f",
+      "\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017",
+      "\u0018\u0019\u001a\u001b\u001c\u001d\u001e\u001f",
+      "\u0020\u0021\u0022\u0023\u0024\u0025\u0026\u0027",
+      "\u0028\u0029\u002a\u002b\u002c\u002d\u002e\u002f"
+    ]
+  },
+  "Person": {
+    "family_name": "Steve:",
+    "given_name": "Stevie",
+    "Organisation": "IMF"
+  }
+}
diff --git a/unittests/table_json_conversion/test_fill_xlsx.py b/unittests/table_json_conversion/test_fill_xlsx.py
index 52416343dbe870bbea23719b9866086b5cbd60aa..8609a6eb919a8af3cd95f0b0cdb347f62a8a6305 100644
--- a/unittests/table_json_conversion/test_fill_xlsx.py
+++ b/unittests/table_json_conversion/test_fill_xlsx.py
@@ -130,12 +130,16 @@ 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"))
-
     fill_and_compare(json_file=rfp("data/indirect_data.json"),
                      template_file=rfp("data/indirect_template.xlsx"),
                      known_good=rfp("data/indirect_data.xlsx"),
                      schema=rfp("data/indirect_schema.json"))
 
+    fill_and_compare(json_file=rfp("data/simple_data_ascii_chars.json"),
+                     template_file=rfp("data/simple_template.xlsx"),
+                     known_good=rfp("data/simple_data.xlsx"),
+                     schema=rfp("data/simple_schema.json"))
+
 
 def test_errors():
     with pytest.raises(AssertionError) as exc: