diff --git a/tests/test_cli.py b/tests/test_cli.py
index 10061a2..28204b2 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -1,6 +1,7 @@
 from click.testing import CliRunner
 from yaml_to_sqlite import cli
 import sqlite_utils
+import json
 
 
 TEST_YAML = """
@@ -8,13 +9,21 @@
   url: https://github.com/simonw/datasette-cluster-map
 - name: datasette-vega
   url: https://github.com/simonw/datasette-vega
+  nested_with_date:
+  - title: Hello
+    date: 2010-01-01
 """
 EXPECTED = [
     {
         "name": "datasette-cluster-map",
         "url": "https://github.com/simonw/datasette-cluster-map",
+        "nested_with_date": None,
+    },
+    {
+        "name": "datasette-vega",
+        "url": "https://github.com/simonw/datasette-vega",
+        "nested_with_date": json.dumps([{"title": "Hello", "date": "2010-01-01"}]),
     },
-    {"name": "datasette-vega", "url": "https://github.com/simonw/datasette-vega"},
 ]
 
 
diff --git a/yaml_to_sqlite/cli.py b/yaml_to_sqlite/cli.py
index 202f21f..61c1ee0 100644
--- a/yaml_to_sqlite/cli.py
+++ b/yaml_to_sqlite/cli.py
@@ -1,6 +1,7 @@
 import click
 import yaml
 import sqlite_utils
+import json
 
 
 @click.command()
@@ -14,4 +15,8 @@
 def cli(db_path, table, yaml_file, pk):
     "Covert YAML files to SQLite"
     db = sqlite_utils.Database(db_path)
-    db[table].upsert_all(yaml.safe_load(yaml_file), pk=pk)
+    docs = yaml.safe_load(yaml_file)
+    # We round-trip the docs to JSON to ensure anything unexpected
+    # like date objects is converted to valid JSON values
+    docs = json.loads(json.dumps(docs, default=str))
+    db[table].upsert_all(docs, pk=pk)