diff --git a/ormar/models/descriptors/descriptors.py b/ormar/models/descriptors/descriptors.py
index 3d168e6..112f49e 100644
--- a/ormar/models/descriptors/descriptors.py
+++ b/ormar/models/descriptors/descriptors.py
@@ -1,6 +1,8 @@
 import base64
 from typing import Any, TYPE_CHECKING, Type
 
+from ormar.queryset.utils import to_str
+
 try:
     import orjson as json
 except ImportError:  # pragma: no cover
@@ -42,7 +44,7 @@ class JsonDescriptor:
     def __set__(self, instance: "Model", value: Any) -> None:
         if not isinstance(value, str):
             value = json.dumps(value)
-        value = value.decode("utf-8") if isinstance(value, bytes) else value
+        value = to_str(value)
         instance._internal_set(self.name, value)
         instance.set_save_status(False)
 
diff --git a/ormar/queryset/utils.py b/ormar/queryset/utils.py
index 1f5a5a3..5520f67 100644
--- a/ormar/queryset/utils.py
+++ b/ormar/queryset/utils.py
@@ -20,7 +20,7 @@ if TYPE_CHECKING:  # pragma no cover
 def to_str(val: Union[bytes, str]):
     """ convert bytes to str simply """
     if isinstance(val, bytes):
-        return val.decode()
+        return val.decode("utf-8")
     return str(val)
 
 
diff --git a/tests/test_queries/test_utils.py b/tests/test_queries/test_utils.py
new file mode 100644
index 0000000..893d4a9
--- /dev/null
+++ b/tests/test_queries/test_utils.py
@@ -0,0 +1,14 @@
+import json
+
+from ormar.queryset.utils import to_str
+
+
+def test_to_str():
+    expected_str = "[]"
+    val = json.dumps([])
+    assert expected_str == to_str(val)
+
+    expected_bytes = expected_str.encode()
+    assert isinstance(expected_bytes, bytes)
+
+    assert isinstance(to_str(expected_bytes), str)