diff --git a/ormar/models/mixins/save_mixin.py b/ormar/models/mixins/save_mixin.py
index 89ddbfe..c0868fb 100644
--- a/ormar/models/mixins/save_mixin.py
+++ b/ormar/models/mixins/save_mixin.py
@@ -23,6 +23,7 @@ import ormar  # noqa: I100, I202
 from ormar.exceptions import ModelPersistenceError
 from ormar.models.mixins import AliasMixin
 from ormar.models.mixins.relation_mixin import RelationMixin
+from ormar.queryset.utils import to_str
 
 if TYPE_CHECKING:  # pragma: no cover
     from ormar import ForeignKeyField, Model
@@ -208,7 +209,7 @@ class SavePrepareMixin(RelationMixin, AliasMixin):
         """
         for key, value in model_dict.items():
             if key in cls._json_fields and not isinstance(value, str):
-                model_dict[key] = json.dumps(value)
+                model_dict[key] = to_str(json.dumps(value))
         return model_dict
 
     @classmethod
diff --git a/ormar/queryset/utils.py b/ormar/queryset/utils.py
index 4ebe07c..1f5a5a3 100644
--- a/ormar/queryset/utils.py
+++ b/ormar/queryset/utils.py
@@ -17,6 +17,13 @@ if TYPE_CHECKING:  # pragma no cover
     from ormar import Model, BaseField
 
 
+def to_str(val: Union[bytes, str]):
+    """ convert bytes to str simply """
+    if isinstance(val, bytes):
+        return val.decode()
+    return str(val)
+
+
 def check_node_not_dict_or_not_last_node(
     part: str, is_last: bool, current_level: Any
 ) -> bool:
diff --git a/tests/test_queries/test_queryset_level_methods.py b/tests/test_queries/test_queryset_level_methods.py
index 449c7df..52cced5 100644
--- a/tests/test_queries/test_queryset_level_methods.py
+++ b/tests/test_queries/test_queryset_level_methods.py
@@ -42,6 +42,7 @@ class ToDo(ormar.Model):
     id: int = ormar.Integer(primary_key=True)
     text: str = ormar.String(max_length=500)
     completed: bool = ormar.Boolean(default=False)
+    pairs: List[str] = ormar.JSON(default=[])
 
 
 class Category(ormar.Model):