@@ -404,7 +404,9 @@ def to_schema(self, t: mi.Type, check_ref: bool = True) -> dict[str, Any]:
                 elif field.default is not mi.NODEFAULT:
                     field_schema["default"] = to_builtins(field.default, str_keys=True)
                 elif field.default_factory in (list, dict, set, bytearray):
-                    field_schema["default"] = field.default_factory()
+                    field_schema["default"] = to_builtins(
+                        field.default_factory(), str_keys=True
+                    )
                 names.append(field.encode_name)
                 fields.append(field_schema)
 
 
@@ -1,6 +1,7 @@
 import datetime
 import decimal
 import enum
+import json
 import sys
 import typing
 import uuid
@@ -373,6 +374,24 @@ class Polygon(msgspec.Struct):
     }
 
 
+@pytest.mark.parametrize(
+    "factory, default",
+    [
+        (list, []),
+        (dict, {}),
+        (set, []),
+        (bytearray, ""),
+    ],
+)
+def test_struct_default_factory_default(factory, default):
+    class Example(msgspec.Struct):
+        x: factory = msgspec.field(default_factory=factory)
+
+    schema = msgspec.json.schema(Example)["$defs"]["Example"]
+    assert schema["properties"]["x"]["default"] == default
+    json.dumps(schema)
+
+
 @pytest.mark.parametrize("forbid_unknown_fields", [False, True])
 def test_struct_array_like(forbid_unknown_fields):
     class Example(